阅读主旨题

ashcroft

main idea我还是经常错。。。
借帖子问一题～～
阅读大全79，第一题：
1.    The passage is primarily concerned
(A) demonstrating why the methods of early seismologists were flawed
(B) arguing that deep events are poorly understood and deserve further study
(C) defending a revolutionary theory about the causes of earthquakes and methods of predicting them
(D) discussing evidence for the existence of deep events and the conditions that allow them to occur
(E) comparing the effects of shallow events with those of deep events

答案为啥是c。。。文章第一段：
In most earthquakes the Earth’s crust cracks like porcelain. Stress builds up until a fracture forms at a depth of a few kilometers and the crust slips to relieve the stress. Some earthquakes, however, take place hundreds of kilometers down in the Earth’s mantle, where high pressure makes rock so ductile that it flows instead of cracking, even under stress severe enough to deform it like putty. How can there be earthquakes at such depths?
最后一句：How can there be earthquakes at such depths? 我认为明显是一个问题解释型的文章，不是新旧观点的对比，后面通篇都在解释这个deep earthquake是怎么去发现，怎么去解释的，哪里有defend a thoery的意思，而且c选项中“ and methods of predicting them”，我觉得文中也没有这个method～～