单项选择题
When entering a foam injected space （） breathing apparatus.
A.put out B.put on C.take off D.take in
单项选择题 The exhaust ports are located around the lower part of the cylinder liner, （）the products of combustion are driven by scavenging air.
单项选择题 The main engine is cooled with fresh water （）is added suitable small quantities of chemicals to prevent corrosion.
单项选择题 （）during the last repair?
