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單項(xiàng)選擇題

A large valve，usually installed above the ram preventers，that forms a seal in the annular space between the pipe and wellbore or，if no pipe is present，on the wellbore itself is called the（）.

A.annular blowout preventer
B.annulus
C.accumulator
D.automatic choke

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單項(xiàng)選擇題

A large metallic device，mounted directly in the piping (usually located at the dock near the point where the vapor hose is attached)，designed to prevent the passage of a rapidly moving flame through the piping is called a（）.

A.flame arrestor
B.flame screen
C.detonation arrestor
D.detonation blocker

單項(xiàng)選擇題

A large basin cut into the shore，closed off by a caisson，and used for dry docking of ships is known as a（）.

A.slipway
B.graving dock
C.ground warp
D.caisson dock

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