Which of the following is a component of emissions-control systems?

The catalytic converter is a critical component of emissions-control systems in modern vehicles. Its primary function is to convert harmful pollutants produced during combustion into less harmful emissions before they exit the vehicle's exhaust system. This device works by facilitating chemical reactions that convert carbon monoxide, hydrocarbons, and nitrogen oxides—common harmful emissions—into carbon dioxide, nitrogen, and water vapor, which are far less damaging to the environment.

The presence of the catalytic converter is essential for compliance with environmental regulations that govern vehicle emissions, making it a key part of the overall emissions-control strategy in any automobile. This role is central to reducing air pollution and promoting cleaner air quality, as it helps to ensure that vehicles meet the necessary emissions standards.

In contrast, while the heating system, air-conditioning system, and transmission are important for vehicle operation and comfort, they do not serve a function related to controlling or reducing emissions.