Answer :
The Exhaust Air Injection (AIR) system is designed to reduce NOx emissions by injecting air into the exhaust and using a catalytic converter to transform pollutants into less harmful substances. So, the correct answer is option D) AIR.
The system designed to reduce nitrogen oxides (NOx) emissions is the Exhaust Air Injection (AIR) system. The AIR system, which is also a component of the exhaust emission control system, injects air into the vehicle's exhaust to help convert NOx into less harmful gases like nitrogen gas (N2) and carbon dioxide (CO2) through the use of a catalytic converter. This process is effective because it reduces the production of NOx by lowering combustion temperatures and limiting the availability of excess oxygen that could lead to more NOx formation. So, the correct answer is option D) AIR.