feifei-16

3smoviesalon

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.

3smoviesalon

A,C,E显然都是错误选项，B是正确的也没什么问题。

不过我觉得D也对啊？题目说了，That angle can be kept fairly stable only by the gravitational influence of Earth’s large, nearby Moon.

都说了ONLY by Moon, 为什么不能推出D选项的，基本不受其它的影响? 是因为题目那句话仅仅是针对Earth而言，所以不能说either Earth's or Mars's吗？还是有别的理解。谢谢～

summertao

我对这个题的理解是：文章是说了MOON的影响，可是没有提到其它星球的影响。所以如果非要去说其它星球没有影响，可能有以偏概全的嫌疑。

3smoviesalon

“所以如果非要去说其它星球没有影响，可能有以偏概全的嫌疑。”

但ONLY by 好像就可以理解为其它的没有影响吧？

MC

>>都说了ONLY by Moon, 为什么不能推出D选项的，基本不受其它的影响? 是因为题目那句话仅仅是针对Earth而言，所以不能说either Earth's or Mars's吗？还是有别的理解。谢谢～
>>但ONLY by 好像就可以理解为其它的没有影响吧？

Based on the statements, We know that:
A) the angle is kept stable because of the substential gravitational influence.
B) The larger the moon, the bigger gravitational influence. (The Moon is large enough to have major impact on Earch while the moons on Mar do not. All other small moons,if any, around Earth does not have substential gravitational influence. Hence Only the Moon has the major gravitational influence on the Earth.

These are the only facts we observe now. We don't know that Gravitational influences other than moons have little or no effect.

For example, if some some day, Human beings can find something else on the planets or create some device which can generate sbustential gravitatinal influence, we can apply that to the Earth and see it tilts more than 23 degree.