—I counted sheep, I drank milk and I tried everything, but nothing helped.

—It seems you _____ too much recently. Try some sleeping pills.

A．worked

B．will be working

C．had worked

D．have been working

电子式防滞刹车回路中，主反馈信号是（）

A、刹车压力

B、机轮转速

C、飞机速度

D、机轮负角加速度