问题补充：
--Did you finish your homework on time yesterday.
--No, I didn on time. By the time I finished it, all my classmates
A. finish it; turned it in
B. finish it; had turned in it
C. make it; turned it in
D. make it; had turned it in
答案：
A. finish it; turned it in
B. finish it; had turned in it
C. make it; turned it in
(答案→)D. make it; had turned it in
解析：make it表示“做到”，故第一空四个选项都正确。而后一空根据时间by the time I finished it表示的是到过去某个时候为止，应用过去完成时；同时rum in是“动词+副词”型短语动词，宾语为人称代词宾格it，应放在rum和in之间。
