16. The axis of Earth’s daily rotation is tilted with respect to the plane of its orbit at an angle of roughly 23 degrees. That angle can be kept fairly stable only by the gravitational influence of Earth’s large, nearby Moon. Without such a stable and moderate axis tilt, a planet’s climate is too extreme and unstable to support life. Mars, for example, has only very small moons, tilts at wildly fluctuating angles, and cannot support life.
If the statements above are true, which one of the following must also be true on the basis of them?
A. If Mars had a sufficiently large nearby moon, Mars would be able to support life.
B. If Earth’s Moon were to leave Earth’s orbit, Earth’s climate would be unable to support life.
C. Any planet with a stable, moderate axis tilt can support life.
D. Gravitational influences other than moons have little or no effect on the magnitude of the tilt angle of either Earth’s or Mars’s axis.
E. No planet that has more than one moon can support life.
我承认B对，但不知道A为什么不对？？谢谢！
A only by B。 A,B到底互为什么条件？是B->A吗？
如果楼主对充分必要条件不甚清楚的话，详见Lawyer的精华贴：
http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=73506&page=2
如果楼主对充分必要条件不甚清楚的话，详见Lawyer的精华贴：
http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=73506&page=2
说的实在是太抽象了，不理解
请参考：
逻辑基础知识 by zeros
http://forum.chasedream.com/dispbbs.asp?boardid=24&star=1&replyid=561865&id=716&skin=0&page=1
一些逻辑的基本概念和规律，老大强力推荐的，不用多说了吧。建议初涉逻辑的XDJM好好看看，清楚思路，弄懂概念，再去做题，能很大程度避免刚开始做题的对什么都模糊和没方向的感觉哦。
Necessary Conditions and Sufficient Conditions - concepts from LSAT official by yws
http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=61430
official LSAT book中对充分条件和必要条件的解释。
Please come in - For those confused by Sufficient and Necessary conditions by valarie
http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=60727
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