瓶式采样器要求进口流速V进等于天然流速V天，否则，当采样器V进

A.含沙量偏大，粒径偏细

B.含沙量偏大，粒径偏粗

C.含沙量偏小，粒径偏细

D.含沙量偏小，粒径偏粗

What does the man hear
[A] He hears someone singing.
[B] He hears someone calling him.
[C] He hears someone calling the woman.