Prep II 21----sc

riri832009

    

Before scientists
learned how to make a synthetic growth hormone, removing it painstakingly
in small amounts from the pituitary glands of human cadavers.

    

 

    

(A) scientists
learned how to make a synthetic growth hormone, removing it painstakingly

    

(B) scientists had
learned about making a synthetic growth hormone, they had to remove it
painstakingly

    

(C) scientists
learned how to synthesize the growth hormone, it had to be painstakingly
removed

    

(D) learning how to
make a synthetic growth hormone, scientists had to remove it painstakingly

    

(E) learning how to
synthesize the growth hormone, it had to be painstakingly removed by scientists

Why C?

dec0412

why not D?

loverwy

A: 主句缺谓语

B: before 从句时态不对。 learn 应该发生在remove之后，所以不能用过去完成时。

D: it代表“a synthetic growth hormone”, 按照原句意思，在学会制作“ a synthetic growth hormone”之前，必须把它除去。既然都没有制作，何以谈的上除去？

E: learning的逻辑主语错误

dec0412

明白了，谢谢哈