An owner of a 12-unit apartment building lived in one of the apartments. the owner refuses to rent to a person because of his national origin. based on federal fair housing laws, does the prospective tenant have a valid complaint?

Yes. You cannot he discriminated against or turned down based on ethnicity or origin alone.

Carbon monoxide is usually more dangerous indoors.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.