What is meant by the term“luffing the boom”of a crane ________．A.Stopping the boomB.Toppin

A.Absorb erosion of high velocity discharge stream

B.Seal pump shaft against entry of air

C.Isolate the outlet side from the inlet side

D.Dampen the turbulent discharge flow

A.It allows for rotation of the hook in the single mode

B.It is required to“twin-up”30-ton pedestal cranes

C.It is used to pick up light loads

D.It is used to rigidly connect two cranes

A.Cranes are able to pick up and drop loads over a greater spotting area

B.Increased safety because the deck is clear of running and standing rigging

C.Simplicity of operation of the crane by its operator

D.All of the above

A.winch speed

B.boom strength

C.load radius

D.cable strength