闪光对焊中，加热焊件主要是靠（）产生电阻热。

An inert gas system installed on a tanker is designed to（）.

A.aid in the stripping and cleaning of cargo tanks

B.increase the rate of discharge of cargo

C.force toxic and explosive fumes from a cargo tank to vent to the outside atmosphere

D.lower the oxygen levels inside cargo tanks, making explosion nearly impossible