女性，19岁，大学一年级新生，从山区来到城市上学：自述不能见马路上的汽车，当汽车经过时，总感觉汽车

In using reduction gears to obtain efficient propeller speeds, _____.

A.they must be located at the after end of the engine

B.they can only be used with one engine at a time

C.they eliminate the need for controllable pitch propellers

D.they are connected to the engine with a flexible coupling

Compared to a constant pitch propeller, a controllable pitch propeller

A.more efficiently uses available engine power

B.operates at a lower efficiency at a fixed speed

C.produces the same torque at lower engine power

D.develops its rated power at a lower speed

Propeller running at ____ are generally efficient.

A.high speeds

B.medium speed

C.low speeds

D.the same speed with the engine

Why a gearbox is needed in a ship driven by a medium-speed diesel engine？ .

A.To reduce the main engine speed

B.To increase the main engine speed

C.To govern the main engine speed

D.To fix the propeller shaft

When ship navigating in rough sea, the correct operation is .

A.navigating with a low diesel engine speed

B.navigating with a stable diesel engine speed

C.increasing the efficiency of propeller

D.increasing fuel injection

A.I + II

B.I ~ III

C.I ~ IV

D.I + II + IV

Propeller pitch speed minus ship speed divided by the propeller pitch speed is termed

A.apparent slip

B.true slip

C.pitch

D.propulsive efficiency

A.four-stroke

B.two-stroke

C.slow speed

D.reversible

A.0.30 to 1

B.3.00 to 1

C.3.33 to 1

D.33.0 to 1