2016-06-23
xredued04
误：I was knowing the answer.
正：I knew the answer. 我知道答案。
误：I wasn't understanding him.
正：I didn't understand him. 我不明白他的意思。
典型例题：
1) Mary ___ a dress when she cut her finger.
A. made B. is making C. was making D. makes
答案C. 割伤手指是已发生的事情，应用过去时。同时，when表时间的同时性，“玛丽在做衣服时”提供事情发生的背景，因此用过去进行时。
2) As she ___ the newspaper, Granny ___ asleep.
A. read; was falling B. was reading; fell C. was reading; was falling D. read;fell
答案B.句中的as = when,
while，意为"当……之时"。描述一件事发生的背景时，用过去进行;一个长动作发生的时候，另一个短动作发生。句意为 "在她看报纸时，奶奶睡着了。"句中的 fell (fall的过去时)，是系动词，后跟形容词，如：fall sick。