If a crankcase explosion occurs in a diesel engine, which of the listed actions should be taken？

It is certain that ______.

A．an object had exploded three miles above the forest

B．the explosion was not caused by a comet

C．an atomic explosion once happened above the ground

D．some form. of life from other planets once visited the earth then

计算机软件有系统软件和应用软件，下列（）属于应用软件。

A.LinuxB.UnixC.Windows 7D.Intenet Explorer

● Windows 操作系统中资源管理器进程可由 （12） 启动。

（12）

A. winlogon.exe

B. wins.exe

C. explorer.exe

D. snmp.exe

What does the speaker say about Yellow Stone national park？

A．It was the first region explored by pioneers.

B．It was the first national park.

C．It is not accessible to everyone.

D．It is not managed by the National Park Service.

The design of the orbiter indicates

A．NASA's determination to continue space exploration.

B．NASA's disadvantage in space technology.

C．the great pressure from Congress on NASA．

D．a heavy defeat for NASA．

A.a shortage of refrigerant in the system

B.air in the system

C.an accumulation of liquid refrigerant in the crankcase

D.a shortage of oil in the crankcase

Crankcase doors should not be opened () the engine has cooled down.

A.after

B.when

C.until

The crankcase can not be opened ______ the parts have been cooled down.

A.if

B.as

C.unless

D.when

If a crankcase explosion occurs in a diesel engine, you should stop the engine and＿.

A.immediately open all crankcase relief ports

B.increase crankcase exhauster speed to draw cool air into the engine

C.allow the engine to cool naturally

D.increase crank case scavenge air to remove unburned gases