—When ___ you ___ the e-dictionary?—Last month.A.have,bought B.had,bought C.do,buy D.did,buy—When ___ you ___ the e-dictionary?—Last month.A.have,bought B.had,bought C.do,buy D.did,buy答案给的是D,但我想知道为什么B不行.

问题描述:

—When ___ you ___ the e-dictionary?—Last month.A.have,bought B.had,bought C.do,buy D.did,buy
—When ___ you ___ the e-dictionary?
—Last month.
A.have,bought B.had,bought C.do,buy D.did,buy
答案给的是D,但我想知道为什么B不行.