Jenny pushed the door again to ______ it ______.

A． make sure if; was closed

B． make sure that; was locked

C． found out it; was shut

D． find out that; was open

外置式汽油压力调节器的作用是使油管中的汽油压力与进气歧管中的气体压力之间的压力差（）。

A.保持恒定

B.随进气歧管内气体压力升高而升高；

C.随进气歧管内气体压力升高而下降