Zhang Heng invented the world’s first water-powered armillary sphere and the world’s first seismometer.

42. According to the relevant regulation, lifeboat should be powered by _______.

To check the setting of the overspeed trip on a diesel powered generator， you would use a （）.

词汇与结构 The flight controls are powered by _________ hydraulic sources: system A and system B.

All ground spoilers are powered by hydraulic system _____ through a control valve and a bypass valve.

The best irrigation water is river water, pond water and lake water A: 正确 B: 错误

What water is used in the production of injection A: pure water B: purified water C: water for injection D: sterile water for injection

According to the distribution of oil, gas and water, the water at the edge of containing edge is called (). A: External water B: Bottom water C: Edge water D: Edge bottom water

Which one is not the common source of injection water: A: surface water B: ground water C: distilled water D: oil polluted water

New York and other U.S. cities have begun using vehicles powered by natural gas