Fresh air and exercise are good for the health.（英译中)

A charge of fresh air is drawn into the engine cylinder and then _____ by the moving piston_____ very high pressure.

.Water and air are _______ to human beings. We can

Open the window and let in some fresh air.（英译中)

In slow speed two-stroke engines, the fresh air entering begins when and stops as .A.the i

根据材料，完成题。Air Transportation1. Airplanes are used to carry passengers， cargo and mai

Such problems______air pollution and traffic jams are becoming more and more serious in so