A self-contained breathing apparatus is used to（）.

A . make underwater repairs to barges B . determine if the air in a tank is safe for men C . enter areas that may contain dangerous fumes or lack oxygen D . resuacitate an unconscious perso

A . 20 minutes B . 15 minutes C . 10 minutes D . 5 minute

A . you are entering a space containing poisonous vapors B . you are entering a space containing explosive gases C . the regulator of the breathing apparatus malfunctions D . the face piece of the breathing device is too tight

A . The unit is working properly B . The face mask is not sealed properly C . The air bottle needs to be refilled D . The air supply hose has a leak

A . Oxygen deficient spaces B . Compartments containing poisonous vapors C . Fighting fires that produce heavy smoke D . Underwater search

A . pressure differences in the atmosphere B . the length of the hose attached to the facepiece C . the physical exertion of the person wearing the device D . spaces containing poisonous vapor

A . a gas mask certified by the Mine Safety and Health Administration B . the same self-contained breathing apparatus required with the fireman's outfit C . an oxygen breathing apparatus，provided that the device has been inspected within three years D . a portable ventilation system that will provide a complete change of air every three minute

A . put out B . put on C . take off D . take i

A . Because carbon dioxide dilutes the oxygen concentration in the atmosphere and may cause asphyxiation B . Because carbon dioxide breaks down in a fire into carbon monoxide which may cause blood poisoning in the person breathing this gas C . Because carbon dioxide is a colorless and odorless gas that becomes highly toxic in the presence of high temperatures and will quickly incapacitate a person exposed to this gas D . This action is unnecessary as carbon dioxide is not poisonous nor toxic but is a relatively harmless ga

A . a centrifugal fan B . a direct expansion cooler C . a hermetic compressor D . a centrifugal pum

A . control the pressure of the oxygen as it enters the body B . allow the wearer to manually give himself oxygen C . release excess heat which would otherwise cause the bottle to explode D . allow exhaled gases to pass outside the bottle

A . administer oxygen B . immediately check his pulse and start CPR C . make the victim comfortable in a bunk D . immediately give a stimulant，by force if necesssary

A . 判断神志 B . 人工循环 C . 开放气道 D . 人工呼吸

A、<p>&nbsp;Because they helped him with his flat tire.</p> B、Because they saved him from a minor car accident. C、<p>Because they showed him the right way back home.</p> D、<p>&nbsp;Because they comforted him and gave him some money.</p>

是 否

B into C.at D.out of

(25) A．Donna should give her friends a chance to explain. B．Donna shouldn't bother to try to change her friends' opinion. C．Donna's friends are too deaf to give any attention to her suggestion. D．Donna should convince her brother to visit her friends.

A．refers to B．defines C．describes D．devotes to