style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/B）October 31st was the eve of the Celtic new year. The Celts were the ancestors of the present-day Irish, Welsh and Scottish people. On this day ghosts walked and mingled with the living, or so the Celts thought. The townspeople baked food all that day and when night fell they dressed up and tried to resemble the souls of the dead. Hoping that the ghosts would leave peacefully before midnight of the new year. Much later, when Christianity spread throughout Ireland and October 31st was no longer the last day of the year, Halloween became a celebration mostly for children. “Ghosts” went from door to door asking for treats, or else a trick would be played on the owners of the house. When millions of Irish people immigrated to the United States in the 1840s the tradition came with them. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/C）Today school dances and neighborhood parties called “block parties” are popular among young and old alike. More and more adults celebrate Halloween. They dress up like historical or political figures and go to masquerade parties(化装舞会). In larger cities, costumed children and their parents gather at shopping malls early in the evening. Stores and businesses give parties with games and treats for the children. Teenagers enjoy costume dances at their schools and the more outrageous the costume the better! Certain pranks(恶作剧)such as soaping car windows and tipping over garbage cans are expected. But partying and pranks are not the only things that Halloweeners enjoy doing. Some collect money to buy food and medicine for needy children around the world. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/D）Halloween originated as a celebration connected with evil spirits. Witches flying on broomsticks with black cats, ghosts, goblins(小精灵)and skeletons have all evolved as symbols of Halloween. They are popular trick-or-treat costumes and decorations for greeting cards and windows. Black is one of the traditional Halloween colors, probably because Halloween festivals and traditions took place at night. In the weeks before October31st, Americans decorate windows of houses and schools with silhouettes(轮廓)of witches and black cats. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/E）Pumpkins are also a symbol of Halloween. The pumpkin is an orange-colored squash. and orange has become the other traditional Halloween color. Carving pumpkins into jack-o'-lanterns is a Halloween custom also dating back to Ireland. A legend grew up about a man named Jack who was so stingy(吝啬的)that he was not allowed into heaven when he died, because he was a miser(吝啬鬼). He couldn’t enter hell either because he had played jokes on the devil. As a result, Jack had to walk the earth with his lantern until Judgement Day. The Irish people carved scary faces out of turnips(芜菁根), beets(甜菜根)or potatoes representing “Jack of the Lantern, ” or Jack-o'-lantern. When the Irish brought their customs to the United States, they carved faces on pumpkins because in the autumn they were more plentiful than turnips. Today jack-o'-lanterns in the windows of a house on Halloween night let costumed children know that there are goodie(糖果)waiting if they knock and say “Trick or Treat!”
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/F）After carving your pumpkin, separate the pulp from the seeds. Rinse the seeds and spread them out to dry. The next day, add enough melted butter or margarine(人造黄油)to coat each seed. Spread the seeds onto a cookie sheet(甜酥饼干)and bake for 20 minutes in a 300 degree oven or until they are slightly brown. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/G）Take the paper wrapping off about l00 caramels and put them in a saucepan(炖锅). Put the saucepan over a pan of boiling water. Boil the water until the caramels melt. Put a wooden stick into the top of each apple, dip the apple into the caramel. Let them cool on wax paper and enjoy!
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/H）No Halloween party is complete without at least one scary story. Usually one person talks in a low voice while everyone else crowds together on the floor or around a fire. The following is a retelling of a tare told in Britain and in North Carolina and Virginia. “What Do YOU Come For?” There was an old woman who rived all by herself, and she was very lonely. Sitting in the kitchen one night, she said, “Oh, I wish I had some company. ”
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/I）No sooner had she spoken than down the chimney tumbled two feet from which the flesh had rotted. The old woman’s eyes bulged with terror. Then two legs dropped to the hearth(壁炉地面)and attached themselves to the feet. Then a body tumbled down, then two alms, and a man’s head. As the old woman watched, the parts came together into a great, tall man. The man danced around and around the room. Faster and faster he went. Then he stopped, and he looked into her eyes. “What do you come for?”  She asked in a small voice that shivered and shook. “What do I come for?” he said. “I come for YOU!” The narrator shouts and jumps at the person near him!

style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/B）Any type of exercise uses your muscles. Running, swimming, weightlifting—any sport you can imagine—uses different muscle groups to generate motion. In running and swimming, your muscles are working to accelerate your body and keep it moving. In weightlifting, your muscles are working to move a weight. Exercise means muscle activity! As you use your muscles, they begin to make demands on the rest of the body. In strenuous exercise, just about every system in your body either focuses its efforts on helping the muscles do their work, or it shuts down. For example, your heart beats faster during strenuous exercise so that it can pump more blood to the muscles, and your stomach shuts down during strenuous exercise so that it does not waste energy that the muscles can use. When you exercise, your muscles act something like electric motors. Your muscles take in a source of energy and they use it to generate force. An electric motor uses electricity to supply its energy. Your muscles are biochemical motors, and they use a chemical called adenosine triphosphate (ATP) for their energy source.
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/C）During the process of “burning” ATP, your muscles need three things: They need oxygen, because chemical reactions require ATP and oxygen is consumed to produce ATP. They need to eliminate metabolic wastes (carbon dioxide, lactic acid) that the chemical reactions generate. They need to get rid of heat. Just like an electric motor, a working muscle generates heat that it needs to get rid of. In order to continue exercising, your muscles must continuously make ATP. To make this happen, your body must supply oxygen to the muscles and eliminate the waste products and heat. The more strenuous the exercise, the greater the demands of working muscle. If these needs are not met, then exercise will cease—that is, you become exhausted and you won’t be able to keep going. To meet the needs of working muscle, the body has an orchestrated response involving the heart, blood vessels, nervous system, lungs, liver and skin. It really is an amazing system! 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/D）For your muscles—in fact, for every cell in your body—the source of energy that keeps everything going is called ATP. Adenosine triphosphate (ATP) is the biochemical way to store and use energy. The entire reaction that turns ATP into energy is a bit complicated, but here is a good summary: Chemically, ATP is an adenine nucleotide bound to three phosphates. There is a lot of energy stored in the bond between the second and third phosphate groups that can be used to fuel chemical reactions. When a cell needs energy, it breaks this bond to form adenosine diphosphate (ADP) and a free phosphate molecule. In some instances, the second phosphate group can also be broken to form adenosine monophosphate (AMP).
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/E）When the cell has excess energy, it stores this energy by forming ATP from ADP and phosphate. ATP is required for the biochemical reactions involved in any muscle contraction. As the work of the muscle increases, more and more ATP gets consumed and must be replaced in order for the muscle to keep moving. Because ATP is so important, the body has several different systems to create ATP. These systems work together in phases. The interesting thing is that different forms of exercise use different systems, so a sprinter is getting ATP in a completely different way from a marathon runner! ATP comes from three different biochemical systems in the muscle, in this order:
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● phosphagen system
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● glycogen-lactic acid system
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● aerobic respiration
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/F）A muscle cell has some amount of ATP floating around that it can use immediately, but not very much--only enough to last for about three seconds. To replenish the ATP levels quickly, muscle cells contain a high-energy phosphate compound called creatine phosphate. The phosphate group is removed from creatine phosphate by an enzyme called creatine kinase, and is transferred to ADP to form ATP. The cell turns ATP into ADP, and the phosphagen rapidly turns the ADP back into ATP. As the muscle continues to work, the creatine phosphate levels begin to decrease. Together, the ATP levels and creatine phosphate levels are called the phosphagen system. The phosphagen system can supply the energy needs of working muscle at a high rate, but only for 8 to 10 seconds.
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/G）Muscles also have big reserves of a complex carbohydrate called glycogen. Glycogen is a chain of glucose molecules. A cell splits glycogen into glucose. Then the cell uses anaerobic metabolism (anaerobic means “without oxygen”) to make ATP and a byproduct called lactic acid from the glucose. About 12 chemical reactions take place to make ATP under this process, so it supplies ATP at a slower rate than the phosphagen system. The system can still act rapidly and produce enough ATP to last about 90 seconds. This system does not need oxygen, which is handy because it takes the heart and lungs some time to get their act together. It is also handy because the rapidly contracting muscle squeezes off its own blood vessels, depriving itself of oxygen-rich blood. There is a definite limit to anerobic respiration because of the lactic acid. The acid is what makes your muscles hurt. Lactic acid builds up in the muscle tissue and causes the fatigue and soreness you feel in your exercising muscles. 
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/H）By two minutes of exercise, the body responds to supply working muscles with oxygen. When oxygen is present, glucose can be completely broken down into carbon dioxide and water in a process called aerobic respiration. The glucose can come from three different places:
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● remaining glycogen supplies in the muscles;
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● breakdown of the liver’s glycogen into glucose, which gets to working muscle through the bloodstream;
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/● absorption of glucose from food in the intestine, which gets to working muscle through the bloodstream.
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/Aerobic respiration can also use fatty acids from fat reserves in muscle and the body to produce ATP. In extreme cases (like starvation), proteins can also be broken down into amino acids and used to make ATP. Aerobic respiration would use carbohydrates first, then fats and finally proteins, if necessary. Aerobic respiration takes even more chemical reactions to produce ATP than either of the above systems. Aerobic respiration produces ATP at the slowest rate of the three systems, but it can continue to supply ATP for several hours or longer, so long as the fuel supply lasts.
style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/ style=margin: 0px; padding: 0px; color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; white-space: normal; background-color: rgb(255, 255, 255);/I）So imagine that you start running. Here’s what happens: The muscle cells burn off the ATP they have floating around in about 3 seconds. The phosphagen system kicks in and supplies energy for 8 to 10 seconds. This would be the major energy system used by the muscles of a 100-meter sprinter or weight lifter, where rapid acceleration, short-duration exercise occurs. If exercise continues longer, then the glycogen-lactic acid system kicks in. This would be true for short-distance exercises such as a 200- or 400-meter dash or 100-meter swim. Finally, if exercise continues, then aerobic respiration takes over. This would occur in endurance events such as an 800-meter dash, marathon run, rowing, cross-country skiing and distance skating. When you start to look closely at how the human body works, it is truly an amazing machine!