标题: prep 一道逻辑指代 [打印本页] 作者: Spencer125 时间: 2013-8-14 15:28 标题: prep 一道逻辑指代 21. (25520-!-item-!-188;#058&002357)
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