A good catalytic converter will typically show a(n) _____ in CO₂ after the converter.

A good catalytic converter is designed to convert harmful emissions such as carbon monoxide (CO) and unburned hydrocarbons into less harmful substances, which ultimately increases the production of carbon dioxide (CO₂). As the engine operates, the catalytic converter facilitates chemical reactions that oxidize carbon monoxide and hydrocarbons, thereby improving the overall combustion process.

When the efficiency of a catalytic converter is high, we would expect to see an increase in the amount of CO₂ in the exhaust gas after it has passed through the converter. This is because more of the carbon from the fuel is being fully oxidized into CO₂ instead of being emitted as CO or remaining unburned hydrocarbons. Thus, a well-functioning catalytic converter contributes to a cleaner exhaust with a higher concentration of CO₂, signaling that the emissions control system is working effectively to reduce pollution.

The other options do not accurately reflect the function of a properly operating catalytic converter. A decrease would suggest that less CO₂ is being produced, which contradicts the idea of better combustion. No change would imply that the converter is not effectively processing the exhaust gases, and fluctuation would indicate inconsistency, which is not typical of a good catalytic converter.