Which of the listed types steam traps operates on the principle that hot water flashes to steam when its vapor pressure is rapidly reduced?（）

A.a gas mask suitable for protection against each refrigerant used, or a self contained breathing apparatus must be provided
B.it is the sole responsibility of the chief engineer to ascertain that all members of the engineering department are familiar with the use of gas masks or breathing apparatus
C.spare charges shall be carried for at least 50% of each size and variety of gas masks and/or self contained breathing apparatus
D.all of the above

A.to inject cleaning additives when the bilges are extremely dirty
B.when the main condenser becomes fouled, in order to provide additional cooling water circulation
C.to connect the rose box to the independent bilge suction
D.if the bilges become flooded and they can not be emptied by any other means

A.frequently grounding out
B.frequently starting and stopping
C.running too fast
D.running too slow