One of the world's first video games,Tetris(俄罗斯方块 ), has turned thirty years old, and its brand is anything but old school.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/But what's kept people swiping and clicking to ensure each row of blocks stays aligned and disappears into the virtual world since its development in 1984 Soviet Russia? A combination of new plat form sand an attracting psychological appeal.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Maya Rogers, the CEO of Blue Planet Software, the sole agent of the Tetris brand, said the protection of the game'score over the last three decades has aided its longevity. As mobile and social become two of the largest sources for gaming these days, Tetris isn't showing any signs of losing its appeal. Currently appearing on over 50 different gaming platforms, from the 1983 Nintendo Entertainment System (NES) to smart phones,Tetris is sold on over 425 million mobile devices. More than 20 billion games of Tetris Battle have been played on Facebook, too. There's some thing psychologically entrancing about the game, that's kept people hooked through the years. "Play a game of Tetris," said Rogers, "and satisfy your craving to create order out of chaos." Plus, there's the added quality of playing Tetris and never feeling wholly fulfilled."There' s no correct move that you can make," said. Neubauer, a loyal player of the game who work as a senior analyst at Saibus Research, an independent research and advisory firm, "The quest for the perfect move never ends."
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Tom Stafford, a professor of cognitive development and psychology at Sheffield University in the U.K., says that Tetris has been around so long because it transports garners into a different realm when they play. "It's a world of perpetually generating uncompleted tasks," he said. As he's said in the past, too, "Tetris is the granddaddy of puzzle games like Candy Crush saga--the things that keep us puzzling away for hours, days and weeks.""Tetris is pure game: thereis no benefit to it, nothing to leam, no social or physical consequence,"he added. "It is almost completely pointless, but keeps us coming back for more."

某交易者以3780元/吨卖出10手白糖期货合约，之后以3890元/吨的价格全部平仓，这笔交易（　）元。(不计手续费等费用)

关于交易手续费，下列说法不正确的是（　）。

style=text-align: justify; style=text-align: justify; style=text-align: justify; style=text-align: justify;

下列关于商品期货合约交易单位的说法，正确的有（　）。

    In August, environmentalists in the Philippines vandalized (肆意破坏 ) a field of Golden Rice, an experimental grain whose genes had been modified. Its seeds will be handed out free to farmers. The aim is to improve the health of children in poor countries by reducing vitamin A deficiency, which contributes to hundreds of thousands of premature deaths and cases of blindness each year.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Environmentalists claim that these sorts of actions are justified because genetically modified crops pose health risks.Now the main ground for those claims has crumbled. Last year a paper which was published in a respected journal found that unusual rates of tumours and deaths in rats that had been fed upon a variety of genetic modification(GM) (转基因) corn.Other studies found no such effects. But this one enabled campaigners to make a health-and-safety argument against GM crops--one persuasive enough to influence governments. After the study appeared, Russia suspended imports of the grain in question. Kenya banned all GM crops. And the French prime minister said that if the results were confirmed he would press for a Europe-wide ban on the GM corn.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    There is now no serious scientific evidence that GM crops do any harm to the health of human beings. There is plenty of evidence, though, that they benefit the health of the planet. One of the biggest challenges facing mankind is to feed the 9 billion-10 billion people who will be alive and richer in 2050. This will require doubling food production on roughly the same area of land, using less water and fewer chemicals. It will also mean making food crops more resistant to the droughts and floods that seem likely if climate change is as bad as scientists fear.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    If the Green revolution had never happened, and yields had stayed at 1960 levels, the world could not produce its current food output even if it ploughed up every last acre of cultivable land.In contrast, GM crops boost yields, protecting wild habitat from the plough.They are more resistant to the vagaries of climate change, and to diseases and pests, reducing the need for agrochemicals. Genetic research holds out the possibility of breakthroughs that could vastly increase the productivity off arming. Vandalizing GM field trials is a bit like the campaign of somereligious leaders to prevent smallpox inoculations: it causes misery, even death, in the name of unscientific belief.

   According to sociologists, there are several different ways in which a person may become recognized as the leader of a social group. In the family, traditional cultural patterns confer leadership on one or both of the parents. In other cases, such as friendship groups, one or more persons may gradually emerge as leaders, although there is no formal process of selection. In larger groups, leaders are usually chosen formally through election or recruitment.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Although leaders are often thought to be people with unusual personal ability, decades of research have failed to produce consistent evidence that there is any category of "natural leaders". It seems that there is no set of personal qualities that all leaders have in common; rather, virtually any person may be recognized as a leader if the person has qualities that meet the needs of that particular group.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Research suggests that there are typically two different leadership roles that are held by different individuals. Instrumental leadership is leadership that emphasizes the completion of tasks by a social group. Group members look to instrumental leaders to" get things done". Expressive leadership, on the other hand, is leadership that emphasizes the collective well-beings of a social group's members. Expressive leaders are less concerned with the overall goals of the group than with providing emotional support to group members and attempting to minimize tension and conflict among them.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Instrumental leaders are likely to have a rather secondary relationship to other group members. They give others and may discipline group members whoinhibit (阻碍) attainment of the group's goals. Expressive leaders cultivate a more personal or primary relationship to others in the group. They offer sympathy when someone experiences difficulties and try to resolve issues that threaten to divide the group. As the difference in these two roles suggest,expressive leaders generally receive more personal affection from groupmembers; instrumental leaders, if they are successful in promoting group goals,may enjoy a more distant respect.