In the last few months， the teachers have given lessons____the Internet as webcasts（主播）．（ ）
| A． |
for |
B． |
at |
C． |
in |
D． |
on |
Don't throw rubbish everywhere，please．Building a civilized（文明的）city is our duty．
_______．（ ）
| A． |
OK，I will |
B． |
You are joking |
| C． |
Take it easy |
D． |
Sorry，I won't |
I saw Susan in the library just now．
No，it __ be her．She went to Shanghai this morning．（ ）
| A． |
must |
B． |
can't |
C． |
may |
D． |
needn't |
You'll get good grades ___ you work hard．（ ）
| A． |
although |
B． |
so |
C． |
if |
D． |
unless |
_______？
I want to buy a pair of sports shoes．（ ）
| A． |
What's wrong |
| B． |
What can I do for you |
| C． |
How much is it |
| D． |
What does it look like |
You'd better ___ more time talking with your parents so that they can understand you better．（ ）
| A． |
spend |
B． |
take |
C． |
cost |