逻辑题

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 B，

A 为什么不对？

原文说了两个因素:大小和角度.   但是大小和角度是否有关系,文章没说.不能单从大小就说M可以support life.而且文章说的大小和角度只是一个必要条件,不是充分条件,就算A中大小和角度都说了,也不能推出M  就一定support life.

谢谢 。 wycg

哦。充分必要性  还是得多 品品啊~

 做题的时候 老是不想！