— There is little water left in the bottle, ______?— No, we need to buy some more before we run out of it.
A:is there
B:isn't there
C:is it
D:isn't it
如图是实验室的部分仪器或实验装置,回答有关问题.
The food safety is a serious _______ in our country. We should try to solve it.
下列关于细胞膜的流动性和选择透过性的叙述,不正确的是( )