When fighting a fire with a portable dry chemical fire extinguisher，the stream should be directed（）.

单项选择题When fighting a fire on a bulkhead using a portable carbon dioxide extinguisher，the stream should be directed at the（）.

A.base of the flames，moving the horn from side to side，following the flames upward as they diminish
B.top of the flaming area，moving the horn from side to side，following the flames downward as they diminish
C.center of the flaming area，moving the horn vertically from top to bottom
D.bottom of the flaming area，moving the horn vertically to the top following the flames upward as they diminish

单项选择题When fighting a fire in an enclosed space，the hose team should crouch as low as possible to（）.

A.protect themselves from smoke
B.obtain the best available air
C.allow the heat and steam to pass overhead
D.All of the above

单项选择题When electrical equipment is involved in a fire，the stream of dry chemicals should be（）.

A.aimed at the source of the flames
B.fogged above the equipment
C.shot off a flat surface onto the flames
D.used to shield against electrical shock

单项选择题When dry chemical extinguishers are used to put out class B fires，there is a danger of reflash because dry chemical（）.

A.is not an effective agent on Class B fires
B.does little or no cooling
C.dissipates quickly
D.is rapidly absorbed by the liquid

单项选择题A shipboard Oil Pollution Emergency Plan is required of（）.

A.all vessels，regardless of size and commercial application
B.any barge or ship constructed or operated in such a manner that no oil in any form can be carried aboard
C.an oil tanker of 150 gross tons and above，or other ship of 400 gross tons and above
D.an oil tanker of 400 gross tons and above，or other ships of 150 gross tons and above