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单选题
Which of the following statements concerning energy is correct?（）
A
Energy can be created or destroyed
B
Energy may not be transformed
C
The total quantity of energy in the universe is always the same
D
None of the above
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单选题Which of the following statements about pump operations is NOT a correct statement?（）A
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A substance must be cold in order for it to be pumpedC
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Special tools are required for lapping or grindingB
It is impossible to throttle flow with a butterfly valveC
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单选题Which of the following statements is true concerning centrifugal pumps?（）A
They are particularly suited for pumping high viscosity fluidsB
They are started with the discharge valve openedC
The flow of liquid is developed by imparting energy due to the rotation of an impellerD
They are always mounted in a horizontal position
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High conductivity of the distillate indicates distillate salinity is excessiveB
Increasing the absolute pressure of the shell will increase the distillers capacityC
Mesh separators are used in evaporators to filter the distillateD
Reducing the brine density will reduce the heat lost overboard
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单选题Which of the following statements is correct concerning a typical shipboard multi-coil refrigeration system?（）A
The liquid receiver functions to collect and remove non-condensable gasesB
A thermostatic expansion valve is used to control refrigerated space temperatureC
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The cetane number affects the amount of injection lagB
The cetane number is an indication of the fuels viscosityC
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单选题Which of the following statements is true concerning Halon 1301 fire extinguishing equipment?（）A
The agent is considered nontoxic at room temperature in low concentrationsB
The agent is less effective than carbon dioxideC
Halon primarily extinguishes the fire by coolingD
The agent cannot be used on electrical fires because it leaves a residue
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单选题Which of the following statements is correct concerning the viscosity of lubricating oil?（）A
Viscosity will increase as temperature increasesB
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单选题Which of the following statements is NOT true?A
Getting off to work with a minimum effort helps save one's energy.B
Dr. Kleitman doesn't explain why people reach their peaks at different hours of the day.C
Habit helps one adapt to his own energy cycle.D
Children have energy cycles, too.
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