2002年诺贝尔物理学奖中的一项，是奖励美国科学家贾科尼和日本科学家小柴晶俊发现

—Can Bill go to the New Year Concert tomorrow?

—_________. He has to study for the math test.[ ]

A. That's right

B. No, he can't

C. Yes, he'd love to

Not until he left his home ______ to know how important the family was for him.

A．did he begin

B．had he began

C．he began

D．he had begun

一个比例调节器其PB=100%，当输入的偏差信号变化10%时，调节器输出的变化是（）。

A.5%

B.10%

C.20%

D.100%

简述如何防止油气中毒。