【简答题】When a sound is made just using air, it is called ‘_____________’; when a sound is made using one’s voice or vibration in the voice box, it is called ‘________’.
【单选题】听力原文:A heater is using convection when it warms the air in a room. And the air in turn warms the people and objects in the room. A hot water radiator, a stove and forced air furnace are all convection...
【单选题】For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should remain constant regardless of load changes? .
【简答题】A) When the warmer air meets with the cooler air. B) When the wind moves faster than 30 meters a second. C) When the seawater evaporates into the air. D) When the air gets wanner and warmer.