单选题When checking the oxygen content of the cargo tanks prior to loading cargoes requiring vapor recovery，the atmosphere must be sampled（）.A one meter from the tank bottom and one meter below the tank topB one half the ullage of the tank and one meter belo

When measuring the oxygen content of the cargo tanks prior to loading cargoes requiring vapor recovery，check it ______.

A.one meter from the tank bottom and one meter below the tank top

B.one half the ullage of the tank and one meter below the tank top

C.one half the ullage of the tank and one meter above the tank bottom

D.at three meter intervals from the tank top to the bottom

Why is gas-freeing rarely required for LPG cargo tanks?

A.LPG is compatible with all cargos

B.LPG's high oxygen content makes it nonvolatile

C.Cargo tanks are inspected less frequently than on oil tankers

D.The cargo tanks are used for one type of cargo only

An inert gas system installed on a tanker is designed to ______.

A.aid in the stripping and cleaning of cargo tanks

B.increase the rate of discharge of cargo

C.force toxic and explosive fumes from a cargo tank to vent to the outside atmosphere

D.lower the oxygen levels inside cargo tanks，making explosion nearly impossible

Valves on steam-smothering lines to cargo tanks shall be set with ______．

A.The master control valve shut and valves to individual cargo tanks shut

B.The master control valve open and valves to individual cargo tanks shut

C.The master control valve shut and valves to individual cargo tanks open

D.All valves open

When discharging an oil cargo，the first consideration is to ______．

A.get the bow up

B.discharge from the wings first

C.discharge from the centerline tanks first

D.discharge from amidships first

In no case shall ballast water be carried in cargo tanks，______ on those rare voyages when weather conditions are so severe that，in the opinion of the master，it is necessary to carry additional ballast water in cargo tanks for the safety of the ship.

A.besides

B.in particular

C.incase of

D.except

Which statement about entry into a space that has been sealed for a long time is TRUE ________．

A.A tank that has been used to carry hazardous liquids should be tested for oxygen content，toxicity，and explosive gases

B.You can safely enter the space without a breathing apparatus if the oxygen content exceeds 14%

C.The natural ventilation through the installed vents is sufficient to provide the proper oxygen content

D.The heat of the sun on upper ballast tanks，such as in a bulk carrier，may generate carbon monoxide

When carrying a cargo of asphalt or molten sulfur，which are carried at temperatures of over 300°F，one of the biggest dangers is ______.

A.water in the tanks or pipelines

B.having the cargo too cool

C.explosion of vapors after discharge

D.inadequate ullage space

Inerting means ______．

A.The introduction of inert gas into a tank with the object of reducing the oxygen content to below 8% by volume

B.The introduction of inert gas into a gas free tank for the purpose of reducing the oxygen content to below 8% by volume

C.The introduction of inert gas into a cargo tank during cargo discharge to replace the volume of discharged cargo

D.All of the above

When the inert gas pressure is being ______ in the cargo tanks，particular attention should be paid to obtaining an oxygen concentration．

A.topped up

B.braced

C.tommed down

D.shored