单选题A cargo boom is a（）.A double sized mattress consists of more than 890 coilsB spar extending from a mast or a king postC flap（Becker rudder）can be fitted to the rudder’s trailing edgeD bridle arrangement having a long beam of the length of the container

What cargo does a jumbo boom or heavy derrick used for lifting?

With a given load on the cargo hook，tension in a single span topping lift ______.

A.increases as the boom's angle to the horizontal increases

B.is at a maximum when the boom is at a 45° angle to the horizontal

C.increases as the boom's angle to the horizontal decreases

D.decreases as the boom's angle to the horizontal decreases

On a crane, the boom indicator tells the operator what angle the boom angle is compared to the ______.

A.vertical position

B.horizontal position

C.boom stop angle

D.minimum radius angle

Sudden starts or stops of the boom is likely to cause all of the following except______．

A.breaking a cargo runner

B.parting guys topping lifts

C.carrying away a block

D.overheating the resistors and eventually burning out

If the cargo gear on your vessel is equipped with a regular guy and a preventer guy，you should ______．

A.Let the schooner guy take most of the strain，thus transferring the load to the opposite boom

B.Leave the preventer guy slack

C.Secure them as close together as possible on deck

D.Secure them so the angle between them is 90° at the boom head

The boom stops are installed on an offshore crane to ______.

A.prevent the boom from being raised too high

B.prevent the boom from swinging

C.support the boom when not in use

D.prevent the boom from being lowered

With a given load on the cargo hook，the thrust on a cargo boom ______.

A.increases as the angle to the horizontal increases

B.increases as the angle to the horizontal decreases

C.is greatest at an angle of 45° and decreases as the boom is raised or lowered

D.is least at an angle of 45° and increases as the boom is raised or lowered

Stress on the topping lift of a swinging boom can be reduced by ______.

A.rigging a back stay

B.raising the boom

C.increasing the mechanical advantage of the cargo purchase

D.taking all slack out of the preventer

When a cargo boom or crane is rated at varying capacities，there will be a table at the controls which relates safe working load to ______．

A.winch speed

B.boom strength

C.load radius

D.cable strength

Which part of a conventional cargo gear rig provides for vertical control and positioning of a boom ________．

A.Cargo whip

B.Gooseneck fitting

C.Spider band

D.Topping lift