The composition and levels of air pollution vary from place to place.

空气污染的成分和程度在各个地方都不尽相同。

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Engine noise is the major noise source of automobile; air power noise is one of composition parts of engine noise.

发动机噪声是汽车的主要噪声源，空气动力噪声是发动机噪声的组成部分之一。

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No one disputes that these globules were formed from stuff melted and thrown into the air by the impact, because their chemical composition matches rock from the crater itself.

ECONOMIST: Some new ideas about why life on Earth has periodic crises

"The text of the Clean Air Act makes plain that Congress intended it as a measure to 'clean' the air of pollutants, not to alter the overall composition of the Earth's atmosphere, " argues the Alliance of Automobile Manufacturers, an auto industry lobbying group, in a brief.

FORBES: Supreme Court Takes On Global Warming?

The Air Force discussions are focused more on whether the military's drone fleet is the right size and composition for future conflicts.

NPR: Military Weighs Cutbacks, Shifts In Drone Programs