When his mother came home, he pretended sound.
| A．sleeping | B．to sleep | C．to have slept | D．to be sleeping |
I'll come to see you if _____.
| A．you're convenient | B．it is convenient for you |
| C．you feel convenient | D．it is convenient with you |
—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 |