when to do和 when doing的区别是什么
问题描述：
when to do和 when doing的区别是什么
答
when doing 当做.事情时 如when doing the exam,we should be careful.实际上这里完整一点的说是这样when （we are） doing the exam,we should be careful.而when to do何时做.如she will tell you when to do it....