问题描述：
谁知道过去进行时的特别用法（一道选择题）
Tom ____ a book about China last year,but i don't know whether he has finished it.
A.has written
B.wrote
C.had written
D.was writing
请说明原因,
Tom ____ a book about China last year,but i don't know whether he has finished it.
A.has written
B.wrote
C.had written
D.was writing
请说明原因,
问题解答：
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