大气中的甲烷有多种来源，包括化石燃料燃烧和农牧业活动，比如奶牛在进食后就会排放这种气体∶-。

It comes from a variety of sources, including fossil fuel production and even farming. Cows give off methane, ya know, after they eat.

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环境中的钒有多种不同来源，人类活动，尤其是大量化石燃料的燃烧，使环境中钒含量急剧增加。

There are many sources of vanadium in environment. Human activities, especially combustion of fossil fuel, make the quantity of vanadium in environment increase intensively.

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燃烧的燃料有固体、液体、气体多种。

Fuels to be burned include solid, liquid, or gaseous fuels.

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