问题
At night, plants _________carbon dioxide and at the same time _________oxygen. So, we may put some in our bedrooms to purify the air.
A:take in, give out
B:take up, give off
C:take in, give in
D:take off, give up;
B:take up, give off
C:take in, give in
D:take off, give up;
正确答案是：
