[单选题]When the electrolyte level of a lead-acid storage battery has decreased due to normal evaporation, the level should be reestablished by adding ______.
[单选题]The stability of a vessel is normally the greatest when all fuel and water tanks are full because the ____.
[单选题]“The use of a poor quality oil can lead to rapid deterioration of its properties with the resultant formation of deposits in the piston crown which in turn results in a considerable reduction in heat transfer with subsequent overheating and thermal cracking.” According to this sentence, we can know that the principle reason of the overheating and thermal cracking is ______.
[单选题]Thermocouples are often used for measuring temperatures. Which of the following descriptions are valid for a thermocouple?
[单选题]Adjustments to the compensating needle valve in a hydraulic governor should be made with the engine at ______.
[单选题]You are installing new piston rings on a single acting diesel engine piston. To check the ring gap clearance, the rings should be placed at the ______.