阀片与阀座密封不严的主要原因?
参考答案:
(1)阀片或阀座密封面不平;
(2)因进气不清洁或积渣引起密封面脏污不平;
(3)阀座密封面损坏。
4×______+8=70÷______+115=220-______×4=120.
Do you think shopping online will ______ take the place of shopping in stores?
A.especially
B.finally
C.frequently
D.exactly