It _______ law for some people to let the children who are not old enough ____ in the factories for them.

Will you drop ________ us tomorrow evening for a talk?—Sounds great! [ ]

Study hard, and will be difficult.

You are leaving your school. How do you like it?——Very much, of course, I ______ this school since I moved here.

The story _________ is not interesting, but why it has so many readers？