Which of the following components is primarily responsible for reducing NOx emissions?

The component primarily responsible for reducing NOx emissions is the exhaust gas recirculation (EGR) system. The EGR system works by recirculating a portion of the engine's exhaust gases back into the intake manifold. This process helps lower the combustion temperature inside the engine, which is critical because high temperatures can lead to the formation of nitrogen oxides (NOx).

When exhaust gases are introduced back into the combustion chamber, they displace some of the oxygen and contribute to a cooler combustion environment. This controlled reduction in temperature minimizes the oxidation of nitrogen, thus significantly curtailing the production of NOx emissions. The effectiveness of the EGR system in achieving these emissions reductions is particularly important in meeting regulatory standards for air quality.

Other choices, while crucial in their own capacities, do not directly target the reduction of NOx emissions in the same way the EGR system does. For example, fuel injectors function primarily to deliver the correct amount of fuel into the combustion chamber for optimal performance and efficiency, but they do not specifically address the NOx emissions. The tailpipe is simply a passage for exhaust gases to exit the vehicle, and the catalytic converter's main role is to convert harmful gases from the exhaust into less harmful emissions (