Oxides of nitrogen in Petrol engine exhaust can be reduced by the following methods:
1. Use of 5% lean mixture
2. Advancing the spark timing
3. Recirculating a fraction of exhaust gas
4. Using an oxidation catalyst in the exhaust manifold
Which of the above statements is/are correct?

A. To prevent pressure build up B. To prevent temperature build up C. To increase the blow by gas D. To reduce the combustion leak

A. Exhaust system and intake system B. Crank case and intake system C. Crank case and exhaust system D. Exhaust system and catalytic converter

A. 20% B. 30% C. 35% D. 40%

A. Throttle body B. Intake manifold chamber C. Intake ports D. Combustion chambers