There will not be enough space to the earth in the future.
A:live on
B:live in
C:live on in
D:live in on
根据污染指数可以判断该天的空气质量状况是( )
— About half an hour's walk.
从生态学的角度来看,下列叙述正确的是( )
下列对免疫概念的叙述正确的是( )