It is difficult for us to learn a lesson in life we’ve in fact had that lesson.
A: does it take you to get to school on foot?B: About Twenty minutes
— in the library!—OK. I'll follow it.
— What animals only come from China?— do.
— Mom, can I have more ice cream?— You can't eat too much.
— What's your father doing?— . He just relaxes (放松) at home.