问题描述：
-Your colleague`s spoken English is beautiful,Lily.-It`s no wonder.She_in the USA for a year
as a visiting professor.
A.worked B.has worked C.had worked D.has been working
选择A 为什么不选B或C
as a visiting professor.
A.worked B.has worked C.had worked D.has been working
选择A 为什么不选B或C
问题解答：
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