题干

I ________ my homework for four hours, but I am not sure whether I   can hand it in tomorrow.
A.have doneB.have been doing
C.had been doingD.had done
上一题 下一题 0.64难度 单项选择 更新时间:2016-05-09 03:41:44

答案(点此获取答案解析)