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问题 选择题

一枚火箭由地面竖直向上发射，其速度-时间图象如图所示，由图象可知 ( )

A．0~ta段火箭的加速度小于ta~tb段的火箭加速度

B．0~ta段火箭是上升过程，在ta~tb段火箭是下落过程

C．tb时刻火箭离地最远

D．tc时刻火箭回到地面

答案

答案：A

题目分析：由图象可知斜率小于的斜率，因此的加速度小于的加速度，故A正确；从图象可知整个过程火箭都在上升，而且在时刻到达最高点，故选项BCD错误．

故选A．

点评：对应图象题目一定明确两个坐标轴的含义，本题中很多学生会错误认为tb时刻火箭到达最高点而且开始下降．

单项选择题

Never mind the obesity epidemic—Canada is (31) with an epidemic of bad ideas on how to fight obesity. The latest is to treat fast-food restaurants as if they were (32) to porn shops, and (33) them from—or at least limit their numbers in—neighbourhoods with schools or hospitals.
That idea is one of many (34) by a group of medical doctors in an article published this week in the Canadian Medical Association Journal. The doctors, (35) by the cardiologist Mark Eisenberg of McGill University, seem to view a bag of potato chips as the moral (36) of a package of cigarettes. They (37) propose the use of graphic warnings for junk food, similar to (38) on cigarette packages," which now have pictures of a dying cancer (39) on them. They would discuss a (40) on junk foods. Salt they suggest removing from processed foods not (41) , so that no one notices, but fast enough to destroy the enticing taste.
There is a logical end to this kind of thinking: men skulking on street corners (42) hamburgers under their trench coats, even as a massive bureaucracy decides how to separate junk foods from (43) ones, for the purposes of launching a fusillade of taxes. (The authors even envision a utopia in which people snack on "trail mix, apple slices and granola bars. ")
Canada does not need a dietitian-in-chief. It doesn’t need healthy-food enforcement officers. People in a democracy should be (44) to make bad choices, even ones as reprehensible as scarfing chips or swilling sugary pop. These choices are different from cigarette smoking, which creates (45) effects on others.

A. therefore B. nevertheless C. again D. even

A new report on children’s inactivity suffers from a similar flaw. Active Healthy Kids Canada complains that 72 percent of youth from the age of 5 to 19 do not have (46) to after-school programs. But why should 19-year-olds, or even the bulk of 14-year-olds, need such regimentation The attitude seems to be that only the government can (47) children from bad habits. How the state is supposed to program the pounds off today’s children is not explained.
Demonizing smoking is very different from demonizing obesity, (48) is a condition, not a behaviour. It is influenced by (49) factors. Shaming and blaming, taxing and banning, will not work. We need to promote greater (50) , at all ages, and all weights, and keep in mind that the heavy hand of the state is not the answer to every ill.
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单项选择题

从事信息安全测评的专门机构是哪个单位？（）

A.软件评测中心

B.信息安全测评中心

C.经信委信息安全处
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