—Tina, is that our math teacher Mr. Wang?
—It ________ be Mr. Wang. He has gone to Beijing.
must
mustn’t
can’t
can
Can you help me ________ up the waste things?
Susan tries ________ English. But she often forgets ________her English book.
You hardly know him, ________ ?
There is ________with the recorder.
________did you surf the Internet this week? Three times.