--- How many concerts ____ up to now?

--- About 25. Last night we ____ our biggest one.

A．did you play, have had

B．have you played, had

C．had you played, have had

D．do you play, have had

说明伯努利方程中各项参数的物理意义。并利用伯努利定理说明气流速度变化与气流压强变化的关系。