Question

there are two primary pre - combustion emissions control systems: the ____ system and the ____ system.

a. exhaust intake recirculation; cooled air intake
b. heated gas recirculation; exhaust air intake
c. heated air intake; exhaust gas recirculation
d. none of the above

Explanation:

Pre - combustion emissions control systems aim to reduce pollutants before combustion. The heated air intake system helps in better fuel - air mixing and combustion efficiency. Exhaust gas recirculation (EGR) is a well - known pre - combustion emissions control method where a portion of exhaust gas is recirculated back into the intake manifold. This helps in reducing the formation of nitrogen oxides ($NO_x$) by lowering the combustion temperature.

Answer:

C. Heated air intake; exhaust gas recirculation