Speaker A: I can't stand the school cafeteriA．The food is terrible. Speaker B:______

A．I agree with you. It's quite difficult to find a seat in the cafeteria.

B．Yeah, you will feel more comfortable if you sit down.

C．Yeah, but that's not the worst thing about it. It's also very dirty.

D．I don't see why they don't supply some seats for us.

在力学单位制中，选定下面哪一组物理量的单位作为基本单位（　　）

A．速度、质量和时间

B．重力、长度和时间

C．长度、质量和时间

D．位移、质量和速度