-What was the party like ?

-Wonderful . It is years _____ I enjoyed myself so much .

A．after

B．when

C．before

D．since

（）分膜片式（阀体上方长的像个蘑菇，可带手轮可不带）和气缸活塞（一般为一正四方长缸体）。

A、减压阀

B、气动阀

C、截止阀

D、闸阀