脑脊液的功能是（）。
A.缓冲压力
B.带走代谢产物
C.维持颅内压
D.运送营养物质
E.保护脑和脊髓
参考答案：A, B, C, D, E
— Are there any boats in the picture?
— _______________[ ]
A. Yes, they are.
B. Yes, it is.
C. No, they aren't.
D. Yes, there is one.
