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 hoe to synthesize the growth hormone, it have to be painstakingly removed by scientists
答案C我選D
答案C的scientist用單數還有被動to be removed讓我作答時選不下去
答案D我覺得沒啥錯誤,learn的主詞是scientists也沒錯,看不太懂原始解釋中說的 從邏輯上來看,句意中的hormone並不是被同一群人使用,而是表述了一種事件之後,hormone就可以怎麼樣怎麼樣了