请教狒狒逻辑一题？

bigmouse

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.
答案是B，A为什么不对？这道题的切入点在哪里？

dorbear

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.
答案是B，A为什么不对？这道题的切入点在哪里？
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本题的切入点就是要提炼出原题的推理模式，真正的考察点就是充分条件和必要条件。

推理模式：sustain life => stable and moderate tilt = large neaby Moon;

这样再根据逆否命题，答案脱颖而出。

（ａ）只是一个逆命题，不必然成立。

dandan74

好分析！

bigmouse

看来，我的阅读还存在很多问题！郁闷！！！