阅读TPO7第一篇的几个问题，做的很崩溃啊，求指教

missrUID: 2722422

The Geologic History of the Mediterranean
Paragraph 3 With question such as these clearly before them, the scientists aboard the Glomar Challenger processed to the Mediterranean to search for the answers. On August 23, 1970, they recovered a sample. The sample consisted of pebbles of gypsum and fragments of volcanic rock. Not a single pebble was found that might have indicated that the pebbles came from the nearby continent. In the days following, samples of solid gypsum were repeatedly brought on deck as drilling operations penetrated the seafloor. Furthermore, the gypsum was found to possess peculiarities of composition and structure that suggested it had formed on desert flats. Sediment above and below the gypsum layer contained tiny marine fossils, indicating open-ocean conditions. As they drilled into the central and deepest part of the Mediterranean basin, the scientists took solid, shiny, crystalline salt from the core barrel. Interbedded with the salt were thin layers of what appeared to be windblown silt.

3．What does the author imply by saying “Not a single pebble was found that might have indicated that the pebbles came from the nearby continent”?
 The most obvious explanation for the origin of the pebbles was not supported by the evidence.
 The geologists did not find as many pebbles as they expected.
 The geologists were looking for a particular kind of pebble.
 The different pebbles could not have come from only one source.
答案是A，我选的B。。。 莫非是要联系上下文，从之前的段落联系？？

4．Which of the following can be inferred from paragraph 3 about the solid gypsum layer?
 It did not contain any marine fossil.
 It had formed in open-ocean conditions.
 It had once been soft, deep-sea mud.
 It contained sediment from nearby deserts.
答案是A，我选的B。。。？？没弄明白

6. What is the main purpose of paragraph 3?
 To describe the physical evidence collected by Hsu and Ryan.
 To explain why some of the questions posed earlier in the passage could not be answered by the findings of the Glomar Challenger.
 To evaluate techniques used by Hsu and Ryan to explore the sea floor.
 To describe the most difficult problems faced by the Glomar Challenger expedition.
答案是A，我选的B。。。。。。。。？？？？？

很是崩溃啊，原本以为这篇做的不错，结果错了好多，，918二战了，大哥大姐帮帮忙啊。。

风行拾UID: 2899495

楼主可以看看这里，有解释：

http://club.topsage.com/thread-2262341-1-1.html

missrUID: 2722422

谢谢谢谢，分析的很到位。。