feifei-16

sylivayjer

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.

请各位大侠指导一下这类题的做法

首先说一下我的思路：must be true means that if it is wrong, then the conclusion is wrong. right?换句话说，没有该选项，就没有答案，所以对每一个选项取非。可是具体应该怎么考虑呢？

dongstar

逆否命题。不要把它看得太难了

liexodus

我觉得反复还是很有必要的，但是要加上及时这个前提

sylivayjer

我总的做了一遍，按分类做了一遍。感觉按分类做后，思路清晰不少。但过了几天，又不清楚了。

我是不是该反复做和看OG？

season5924

你有没有总结过OG里面各种题目的类型呢？

我没有看过feifei，也没有看过LSAT。有人说lsat和gmat的套路不一样，看了没多大的用处。

建议你花时间自己整理一下og的题目类型，慢慢会品出味道的。

gwd的题目是真题，而且是近年的题目，更有价值的。

sylivayjer

两位大侠，我已经做了OG*2遍，费费两遍，以及一些GMATLSAT的逻辑，为什么还是没有很清晰。请教二位如何提高，还有什么有用的材料，以及针对这些题型的解题思路

ozymendias

If Earth’s Moon were to leave Earth’s orbit -----〉That angle cannot be kept fairly stable ---à

a planet’s climate is too extreme and unstable to support life.( based on Without such a stable and moderate axis tilt, a planet’s climate is too extreme and unstable to support life.)

(B) If Earth’s Moon were to leave Earth’s orbit, Earth’s climate would be unable to support life.

Is correct!

此题为典型的逻辑关系推理题。

season5924

选B吧。

原文的推导过程：only by moon -> angle/tilt; no tilt -> no life

所以，no moon->no tilt->no life B正确。

A, C不充分；D,E与原题无关。