Can someone see this question

nikema

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 examplr, has only only very small moons, tilt at wildly fluctualing angles, and cannot support life.
If the statement above are true, which one of the following must also be true on the basis of them.
A). If Mars had a sufficient large nearly 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 influence other than moons have little or no effect on the magnitude of tilt angle of either Earth's or Mar's axis.
E). No planet that has more than one moon can support life.
CAn any one help me to see whether my analysis is right or not.
The first and second sentences are evidence or premises, the third sentence is a conclusion.( there is no exact word about conclusion  Last sentence as a example supports the conclusion. So from the third sentence can infer that c is right!

nikema

I am sorry, b is right!

kathy72

这是一个关于充分条件和必要条件的题目.

.Without such a stable and moderate axis tilt, a planet's climate is too extreme and unstable to support life 等同于:
only if such a stable and moderate axis tilt exits(B), can a planet's climate support life(A) .


从这句话, 我们可以推出转轴的倾斜是支持生命的必要条件. 即A-->B

而C选项将其当成了充分条件.

B选项说月量偏离轨道, 也就是转轴倾斜的条件不成立, 即非B ---> 非A, 正好是A-->B 的逆否命题, 因此正确.

nikema

Thanks!