—Dad，why must I stop ________ computer games？
—For your health，my boy．
| A．play |
| B．to play |
| C．to playing |
| D．playing |
-Who is in the classroom? -_________.
A. None B. No one C. No
-How many books are there in the box?
-_______.
A. None B. No one C. No
There _________a book and three pens on my desk just now，but now there is nothing on it.
A. had B. were C. was
Nobody except Tom and Mary _______in the classroom. The other students are watching the basketball game on the playground now.
A. am B. is C. are
How time flies! We'll graduate. Three years really s short time.
A. was B. are C. is