—I’m not sure ______there are living things on other planets or not .
—Even scientists aren’t sure about it.
| A．where | B．why | C．what | D．whether |
Tony is really funny, he often makes me _______.
A. laugh B. laughs C. laughed
There will be less_______ and the environment will be better.
A. trees B. pollution C. factories
Tom ran _______ Sam. They are both winners.
A. as quickly as
B. as quick as
C. so quickly as
—_______ does Mary surf the Internet?
— Every day.
A. How long B. How many C. How often
Mr. Li is one of _______ best engineers in this factory.
A. the B. an C. A