问题描述：
一个简单的英语填空题
Homework _ on time will lead to better grades.
A.done B.be done C.having done D.to have been done
最好能说说是什么原因,
Homework _ on time will lead to better grades.
A.done B.be done C.having done D.to have been done
最好能说说是什么原因,
问题解答：
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