问题补充：
－Excuse me, does Mr Smith’s son live here?
－He be here, but he has moved.
A. has to
B. used to
C. tried to
D. happened to
答案：
A. has to
(答案→)B. used to
C. tried to
D. happened to
解析：A. has to 不得不 B. used to过去常常 C. tried to 尽力 D. happened to碰巧发生；句意：打扰了，请问史密斯先生的儿子住在这里吗？他过去住在这里，但是已经搬走了。故选B
