carbon monoxide is present in\na the exhaust gases of vehicles with loud mufflers only.\nb all exhaust gases…

Brief Explanations:

Carbon - monoxide is a by - product of incomplete combustion in gasoline engines. All gasoline engines produce some carbon monoxide in their exhaust gases due to the nature of the combustion process. Loud mufflers, poor maintenance, and vehicle age can affect the amount but not the presence.

Answer:

B. all exhaust gases from all gasoline engines