A safe fuel system must（）.

单项选择题A large vessel is equipped with a controllable pitch propeller. Which statement is TRUE?（）

A.When dead in the water，it is often difficult to find the neutral position and slight headway or sternway may result
B.When going directly from full ahead to full astern，there is complete steering control
C.When the vessel has headway and the propeller is in neutral，there is no effect on rudder control
D.When maneuvering in port，full ahead or astern power can usually be obtained without changing shaft RPM

单项选择题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

单项选择题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

单项选择题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

单项选择题A jack-up drilling unit elevated on the Outer Continental Shelf must have a fog horn that will sound（）.

A.a 2-second blast every 20 seconds
B.a 4-second blast every 20 seconds
C.an 8-second blast every 30 seconds
D.a 10-second blast every 30 seconds