问题补充:
-----Tom. You look very bored and tired.
-----Yes, I my father on the farm until seven o’clock this morning.
A. have been helping
B. had helped
C. was helping
D. am helping
答案:
A. have been helping
B. had helped
(答案→)C. was helping
D. am helping
解析:由表示过去的时间状语until seven o’clock this morning可知, 前面用过去进行时。本题注意不要受思维定势的影响而用现在完成进行时,要深入体会动作的时间性。