飞机上升和下降时，服务员向乘客递送糖果，使乘客做吞咽动作，其生理意义在于

A．调节基底膜两侧的压力平衡

B．调节圆窗膜内外压力平衡

C．调节前庭膜两侧的压力平衡

D．调节鼓室与大气之间的压力平衡

E．调节中耳与内耳之间的压力平衡

We're tired because we have________yin. [ ]

A. too many

B. too much

C. many too

D. much too