语法题请教

是以前摘录的,无法知道出处了.非常对不起不能用统一格式.

1.By studying fossils, paleontologist learn ___ forms of life thrived during various period of the earth's history.

A.from

B.so

C.the.

D.what

答案D. 为什么?为什么不是C.

2. Beginning in the middle Ages, composers of western music used a system of notating their compositions ___ be performed by musicians.

A. will

B.that.

C.and when to

D. so they could

答案D. 怎么不是so that they could?

3. The production of tin ore in the United States is relatively insignificant,  ___less than one hundred tons annually.

A. amounting to

B. in the amount

C. amounts to it

D. to the amount of

答案A, 为什么B,D不对?

谢谢.前二题没问题了.第三题还有点疑问,麻烦再看看:

第三题的B,不是可以扩展成in the amount (which is ) less than....which is 省略.

A中to 是介词,D中of也是介词,to 能用,of应该也能用吧.

对于amount 本身来讲，若表示总计，只能是amount to这个词组，amount of就是数量的意思了，从句意来看，这里表示总计恰当，Ａ好

若照ＪＪ那样改in the amount (which is ) less than，带入正个句子，似乎结构就不和惯用法，若那样，偶认为这句应这样说The production of tin ore in the United States is relatively insignificant,  the amount of which is less than one hundred tons annually.

amount若做了后句的中心词，前用ＩＮ似乎说不过去．ＪＪ再想想看

ＯＦ确实是介词，但ＴＯ和ＯＦ再语意上还是有区别的，有时看词性外，还的看一下意思，加上他们词组意思都不一样了．

请教两道语法改错题:

(1)  Troops (housing) in Fort Bliss ,Texas.(train) to (operate) aircraft (equipment) and artillery.

(2)  The (philosophers) and artists of ancient Greece and Rome (emphasized the) study of (human as)  (fundamental to) their doctrine.