單項選擇題If a liquid sight flow indicator in a refrigeration system shows gas bubbles in motion passing inside of the glass, there is （）.

A.too much refrigerant in the system
B.oil entrained in the refrigerant
C.less than a full charge of refrigerant in the system
D.ice crystals forming in the refrigerant


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1.單項選擇題Dual electro-hydraulic steering units usually operate （）.

A.with both pumps on line at the same time
B.with one pump on standby
C.with the follow-up gear disconnected
D.only when the rudder is moved amidships

2.單項選擇題One distinct advantage of flash type evaporators, as compared to most other evaporators, is that in a flash evaporator （）.

A.high temperature distillate can be re- circulated to induce additional flashing
B.scale formation is not a severe problem
C.cold shocking is more effective in removing scale
D.water purity is greatly increased at high capacity

3.單項選擇題A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently chargedIt is generally located in the（）.

A.high pressure liquid line
B.low pressure liquid line
C.high pressure vapor line
D.low pressure vapor line

4.單項選擇題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

5.單項選擇題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