请教一道feifei逻辑里的题目

ba80403

16. The axis ofEarth’s daily rotation is tilted with respect to the plane of its orbit at anangle of roughly 23 degrees. That angle can be kept fairly stable only by thegravitational influence of Earth’s large, nearby Moon. Without such a stableand moderate axis tilt, a planet’s climate is too extreme and unstable tosupport life. Mars, for example, has only very small moons, tilts at wildlyfluctuating angles, and cannot support life.

If thestatements above are true, which one of the following must also be true on thebasis of them?

A.      If Mars had a sufficientlylarge nearby moon, Mars would be able to support life.
B.       If Earth’s Moon were to leaveEarth’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 otherthan moons have little or no effect on the magnitude of the tilt angle ofeither Earth’s or Mars’s axis.
E.       No planet that has more thanone moon can support life.
答案是B，我觉得不对，这里根本没有提到moon是在earth的orbit上，只是说有了moon的影响而使得earth的orbit与axis保持 23度。所以我觉得应该选择A
烦请高手指点一下！！

sdcar2010

formal logic.

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.

Premise:

1) Angle/tilt stable --> Moon

2) If tilt/angle not stable --> unstable to support life.

B) No Moon --> angle/tilt not stable --> unstable to support life