The reason ______ most Chinese have healthy white teeth is ______ they eat a healthy diet.
| A．why; that | B．why; because | C．that; that | D．for; that |
—Must I turn off the gas after cooking ?
—Of course . You can never be _______ careful with
that.
| A．enough | B．too | C．so | D．very |
_____ is known to everybody, the moon travels round the earth once every month.
| A．It | B．As | C．That | D．What |
It is so difficult a problem that _____ student in this class _____ work it out.
| A．any, can't | B．no, can | C．every, can | D．no, can't |
Shirley _____ a book about China last year, but I don't know whether she has finished it.
| A．has written | B．wrote | C．had written | D．was writing |
Who did the teacher have ___ an article for the wall newspaper just now?
| A．written | B．writing | C．write | D．to write |