she often kept the office clean when she was at work.这个句子对吗,为什么

题目

she often kept the office clean when she was at work.这个句子对吗,为什么
原题是这样的：she often -the office -when she was at work.
A.for making；to Bto make ;of Cfor making;at Dfor making;for

答案

不对,时态上这是一个常态的话（用了often）就应该用一般现在时she often keeps the office clean when she is at work.或者去掉often,改成she used to keep the office clean when she was at work.（过去常常） she...