Final answer:
Nitrogen oxides are created during combustion, and low oil temperature can increase the tendency for nitration. A catalytic converter helps to convert harmful materials into less harmful ones, making B and C true statements. Nitration relates to oil degradation, not directly to engine problems.
Step-by-step explanation:
The true statements from the choices provided about nitrogen oxides (NOx) and combustion in gas engines are:
Nitrogen oxides (NOx) are created during combustion.
Low oil temperature increases nitration tendency.
Nitration can be a problem in gas engines, especially when certain factors such as low oil temperatures that prevent complete combustion occur, leading to increased formation of nitrogen oxides. These are compounds like nitrogen dioxide (NO₂) which contribute to smog and acid rain, which are problematic for gas engines.
A catalytic converter in the exhaust system helps in converting these harmful materials into less harmful products. Hence, statement B and statement C are true. As for statement A, nitration is more commonly associated with oil degradation rather than being a direct issue in engine operation.