OG上一道阅读题

WWOWUID: 3649627

Saturn’s giant moon Titan is the only planetary satellite with a significant atmosphere and the only body in the solar system other than Earth that has a thick atmosphere dominated by molecular nitrogen. For a long time, the big question about Titan’s atmosphere was how it could be so thick, given that Jupiter’s moons Ganymede and Callisto, which are the same size as Titan, have none. The conditions for acquiring and retaining a thick nitrogen atmosphere are now readily understood. The low temperature of the protosaturnian nebula enabled Titan to acquire the moderately volatile compounds methane and ammonia (later converted to nitrogen) in addition to water. The higher temperatures of Jupiter’s moons, which were closer to the Sun, prevented them from acquiring such an atmosphere.

According to the passage, Titan differs atmospherically from Ganymede and Callisto because of a difference in

A rate of heat loss

B proximity to the Sun

C availability of methane and ammonia

D distance from its planet

E size

答案是B， 想问一下C为何不对呀？ 文章中也说了Titan可以acquire the moderately volatile compounds methane and ammonia，纠结中 求解救=。= 谢谢了

minnie_silenceUID: 2645012

B是最根本的原因。
Titan可以acquire那些气体是因为离太阳远。

gterlannUID: 3595027

这里的moderately指的是:in a moderate temperature,意思是这里的温度并不moderate,也就是温度很低;
acquire在这里的意思并不是get access to,在用于对挥发性气体的使用上,一般指capture and hold,参考volatile释义:
1. : readily vaporizable at a relatively low temperature
5. : difficult to capture or hold permanently : evanescent, transitory

所以availability是irrelevant的

WWOWUID: 3649627

minnie_silence 发表于 2015-10-10 17:11
B是最根本的原因。
Titan可以acquire那些气体是因为离太阳远。

谢谢啦

WWOWUID: 3649627

gterlann 发表于 2015-10-10 18:18
这里的moderately指的是:in a moderate temperature,意思是这里的温度并不moderate,也就是温度很低;
acqui ...

好的明白了谢谢哈:)