The correct answer is: A.Oxygen.
Oxygen is a natural component of the air and does not contribute to air pollution. In fact, it is essential for life on Earth.
The other options, however, are common contributors to air pollution:
B.CFCs (Chlorofluorocarbons): These chemicals were used in refrigerants and aerosols but are harmful to the ozone layer and contribute to global warming, thus playing a role in air pollution.
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