问题描述：
求教一道英语选择题.
Sometimes it is necessary to be careful _______ the right date to sit for a test.
A.when choosing B.when you will choose
C.when you have chosen D.when you chose
应该选哪一个?为什么呢?
Sometimes it is necessary to be careful _______ the right date to sit for a test.
A.when choosing B.when you will choose
C.when you have chosen D.when you chose
应该选哪一个?为什么呢?
问题解答：
我来补答展开全文阅读