When required to work where there may be explosive gases, you should use tools which are （）

A.the forced ventilating system is operating
B.the cargo pumps are secured
C.no monocarbon gases are present
D.the oily water separator is de-energized

A.signaling that all personnel are clear before lifting or lowering material
B.Examining material for sharp edges or protruding points before handling
C.Closing, tagging, or securing valves that permit entrance of steam, water, or air into a fitting or other equipment
D.Throwing materials from high places to the deck

A.The expansion tank should be topped off
B.The thermostatic water regulating valves should be manually opened
C.The fuel filters should be changed
D.The engine should be turned over slowly with the indicator cocks open