问题补充：
Mr. Bo for half a month. He’ll come back in two months.
A. left
B. leave
C. has left
D. has been away
答案：
A. left
B. leave
C. has left
(答案→)D. has been away
解析：句意：Bo先生已经离开了半个月了，两个月之后他将回来。句中有表一段时间的状语for half a month，谓语动词要有延续性，leave 改为be away,故选D.
