Scientists have advanced many theories about why human beings cry tears，none of ______ has been proved．（ ）
| A． |
whom |
B． |
which |
C． |
what |
D． |
that |
She asked me _______ I had returned the books to the library, and I admitted that I hadn't.
| A． |
when |
B． |
where |
C． |
whether |
D． |
what |
-I want to see Mr. White. We have an appointment.
-I'm sorry, but he is not ________ at the moment, for the meeting hasn't ended.
| A． |
busy |
B． |
active |
C． |
concerned |
D． |
available |
My room is a mess, but I __________clean it before I go out tonight. I can do it in the morning.
| A． |
daren't |
B． |
shouldn't |
C． |
needn't |
D． |
mustn't |
-Albert's birthday is on next Saturday, and I'm planning a surprise party for him.
-__________. I'll bring some wine.
| A． |
Sounds like fun |
B． |
It depends |
| C． |
Just a minute |
D． |
You are welcome |
--Going to watch the Women's Volleyball Match on Wednesday?
--_________! Will you go with me?
| A． |
You there |
B． |
You bet |
C． |
You got me |
D． |
You know better |