The air fuel ratio required for the efficient operation of a three way converter is approximately

The question asks about the ideal air-fuel ratio for a three-way converter.
A three-way converter is used in vehicles to reduce harmful emissions.
It works most efficiently when the engine operates at a stoichiometric air-fuel ratio.
The stoichiometric air-fuel ratio is the perfect mixture where all the fuel and oxygen are consumed completely.
This ratio is approximately 14.7:1, which is closest to 15:1 among the given options.
Therefore, the correct answer is Option C: 15:1.
The other options are incorrect because they represent air-fuel ratios that are either too rich (5:1, 10:1) or too lean (20:1) for optimal three-way converter operation.