Which of the following is an example of a natural source of air pollution? a. burning coal releases carbon dioxide. b. cows release methane gas during digestion. c. plowing crops releases dust particles. d. mining releases solid particles into the air.

 Cows releasing methane from their digestion process is an example of natural air pollution.  Natural air pollution results from activities which human beings have got no control over them.  They are mostly ordered by nature and it is not possible to stop or control them. Since the methane gas resulting from the digestion process of the cow is a biological occurrence which is natural, it can therefore be considered to be a natural air pollution.

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.

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