How do many indoor environments generally compare to outdoor environments in terms of pollution?

/in /by

How do many indoor environments generally compare to outdoor environments in terms of pollution?

a.  Indoor environments are much less polluted than outdoor environments.

b.  Indoor environments are slightly less polluted than outdoor environments.

c. Indoor environments contain the same levels of pollutants as outdoor environments.

d. Indoor environments are slightly more polluted than outdoor environments.

 e. Indoor environments are much more polluted than outdoor environments.

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