本初子午线是（）
A.东西两半球的分界
B.东经与西经的分界
C.计算纬度的起始线
D.日期界线
参考答案：B
解析：
本初子午线是0°经线，是东西经度的分界线，B正确，C错；东西半球的分界线是20°W和160°E，A错；日期界限有自然日界线和人为日界线，人为日界线是以180°经线为基准的，而自然日界线是不固定的，为24时（或0时）所在经线，故D错。
考点：本初子午线的意义
You have often __1__ people talk about work. Perhaps you have __2__ your friends about how hard you worked to get something done. However, you may have done no work __3_ you think you worked hard. A boy is pushing a big box very hard, but the box is __4__ heavy for him to move and he may __5__ to push against the box. __6__ the language of science, he has not done __7__ work. Can you think you are working when you are studying or talking? In science, work is only done when a force(力) moves something that has weight through a distance（距离）. Work =" force" × distance moved. __8_ you want to find out whether work is done, _9_ yourself, “Is a push or a pull moving something through a distance?” If your answer is __10_, then work is being done.
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