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问题 单项选择题

2007年我国粮食种植面积10553万公顷，比上年增加70万公顷；棉花种植面积559万公顷，增加7万公顷；油料种植面积1094万公顷，减少60万公顷；糖料种植面积167万公顷，增加10万公顷。

全年粮食产量50150万吨，比上年增加350万吨，增产0.7%，其中，夏粮产量11534万吨，增产1.3%；早稻产量3196万吨，增产0.3%；秋粮产量35420万吨，增产0.6%。

全年棉花产量760万吨，比上年增产1.3%。油料产量2461万吨，减产4.2%。糖料产量 11110万吨，增产11.4%。烤烟产量239万吨，减产3.9%。茶叶产量114万吨，增产10.9%。全年肉类总产量6800万吨，比上年减少3.5%。其中，猪肉减少9.2%；牛、羊肉分别增长 6.1%和5.8%。全年水产品产量4737万吨，增长3.3%。全年木材产量6974万立方米，增长5.5%。

2007年我国粮食平均亩产量约为（1公顷＝15亩）（）。

A．475公斤

B．416公斤

C．368公斤

D．317公斤

答案

参考答案：D

解析：

由图表数据可知，2007年粮食平均亩产量是：50150万吨÷(10553万公顷×15)亩≈317(公斤)，注意单位的换算。

选择题
下列命题中是真命题的是（　　）
①“若x2+y2≠0，则x，y不全为零”的否命题；
②“正多边形都相似”的逆命题；
③“对∀x＞0，都有x＞lnx”的否定；
④“若x-3
1
2
是有理数，则x是无理数”的逆否命题．
A．①②③④B．①③④C．②③④D．①④
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单项选择题

Passage Three

For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic (国家主义的). Columbus went west to look for better trade routes to the Orient and to promote the greater glory of Spain. Lewis and Clark journeyed into the American wilderness to find out what the U. S. had acquired when it purchased Louisiana, and the Appolo astronauts rocketed to the moon in a dramatic show of technological muscle during the cold war.
Although their missions blended commercial and political military imperatives, the explorers involved all accomplished some significant science simply by going where no scientists had gone before.
Today Mars looms (隐约出现) as humanity’s next great terra incognita (未探明之地). And with growing emphasis on international cooperation in large space ventures, it is clear that imperatives (需要，必要) other than profits or nationalism will have to compel human beings to leave their tracks on the planet’s reddish surface. Could it be that science, which has long played a minor role in exploration, is at last destined to take a leading role The question naturally invites a couple of others: Are there experiments that only humans could do on Mars Could those experiments provide insights profound enough to justify the expense of sending people across inter- planetary space
With Mars the scientific stakes are arguably higher than they have ever been. The issue of whether life ever existed on the planet, and whether it persists to this day, has been highlighted by mounting evidence that the Red Planet once had abundant stable, liquid water and by the continuing controversy over suggestions that bacterial fossils rode to Earth on a meteorite (陨石) from Mars. A more conclusive answer about life on Mars, past or present, would give researchers invaluable data about the range of conditions under which a planet can generate the complex chemistry that leads to life. If it could be established that life arose independently on Mars and Earth, the finding would provide the first concrete clues in one of the deepest mysteries in all of science: the prevalence of life in the universe.

By saying "With Mars the scientific stakes are arguably higher than they have ever been" (Line 1, Para.4), the author means that______.

A．with Mars the risks involved are much greater than any previous space ventures

B．in the case of Mars, the rewards of scientific exploration can be very high

C．in the case of Mars, much more research funds are needed than ever before

D．with Mars, scientists argue, the fundamental interests of science are at issue
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