（）是利用液流流经缝隙产生的压力降的原理，使阀的出口压力低于进口压力的压力控制阀。
参考答案：减压阀
为什么规定发展党员要有两名正式党员作入党介绍人？
— I ____ to be here on time, sir.
— But you ____ late again. [ ]
A. meant; are
B. meant; had been
C. have meant; were
D. have meant; are
