问题描述：
He works as a teacher now,but he ___ on a farm for 3 years.A.worked B.has worked C.had worked D.wo
He works as a teacher now,but he ___ on a farm for 3 years.
A.worked B.has worked C.had worked D.wokes
答案给的是A,但是为什么不能选C过去完成时呢?他现在的工作是作为一名老师,但是他曾经在农场干了三年.
还有我想知道为什么farm前面的介词是on,shcool、hospital等前面都是in啊.
He works as a teacher now,but he ___ on a farm for 3 years.
A.worked B.has worked C.had worked D.wokes
答案给的是A,但是为什么不能选C过去完成时呢?他现在的工作是作为一名老师,但是他曾经在农场干了三年.
还有我想知道为什么farm前面的介词是on,shcool、hospital等前面都是in啊.
问题解答：
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