tpo8-3阅读求助

coolshevaUID：3080647

TPO8 RUNNING WATER ON MARS

Paragraph 2 Outflow channels are probably relics of catastrophic flooding on Mars long ago. They appear only in equatorial regions and generally do not form extensive interconnected networks. Instead, they are probably the paths taken by huge volumes of water draining from the southern highlands into the northern plains. The onrushing water arising from these flash floods likely also formed the odd teardrop-shaped “islands” (resembling the miniature versions seen in the wet sand of our beaches at low tide) that have been found on the plains close to the ends of the outflow channels. Judging from the width and depth of the channels, the flow rates must have been truly enormous―perhaps as much as a hundred times greater than the 105 tons per second carried by the great Amazon river. Flooding shaped the outflow channels approximately 3 billion years ago, about the same times as the northern volcanic plains formed.

6. According to paragraph 2, all of the following are true of the outflow channels on Mars EXCEPT:
○They formed at around the same time that volcanic activity was occurring on the northern plains.
○They are found only on certain parts of the Martian surface.
○They sometimes empty onto what appear to have once been the wet sands of tidal beaches.
○They are thought to have carried water northward from the equatorial regions.

答案是c，但是a和d也不对啊。
与a对应的是最后一句，但文中的时间点是火山平原形成的时间，而a选项是火山活动的时间。
与d对应的 是draining from the southern highlands into the northern plains，并不是 northward from the equatorial regions。
求大神指导，顺便解释一下选项c的意思。

coolshevaUID：3080647

black_marble 发表于 2012-9-23 19:09
http://blog.sina.com.cn/s/blog_732869e601012mzf.html

这个上面的解释你可以看看

谢谢回答，这个我看过，不过解释的很牵强