横式采样器能在不同水深和含沙量条件下取得（）水样。
A、瞬时
B、积时
C、时均
D、历时
参考答案：A
—You look very sad. What's wrong?
—Don't worry. There is _______.[ ]
A. something serious
B. serious something
C. nothing serious
D. serious nothing
什么是国际收支的经常差额、基本差额和总差额？这些差额又是如何调剂的？
