11. 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. scientist 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 have to be painstakingly removed by scientists
Ans C
我不懂為什麼D不對
OG不是慣用 D 連接詞+V-ing..., S+V 這種用法嗎
而且D主動不事也比較好嗎
請教大大們幫忙解惑 感激不盡!!