Monday morning he wrote an article on grammar. Monday morning he had written an article

发布时间：2020-08-14 23:47:12

     Monday morning he wrote an article on grammar. 
     Monday morning he had written an article on grammar. 
A. By
B. On
C. At
D. ／

网友回答

A. By
(答案→)B. On
C. At
D. ／
解析：A.用on（at）＋过去时间状语,句子用过去时；by＋过去时间状语,句子用过去完成时.
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