ANS:B - 12 : 1

The air-fuel ratio for maximum power generation in a spark ignition engine, such as a gasoline (petrol) engine, is typically around 12:1. This ratio represents the mass of air to the mass of fuel in the mixture entering the engine's combustion chamber. At an air-fuel ratio of around 12:1, the mixture is optimized to provide maximum power output while ensuring efficient combustion and minimal emissions. It's worth noting that the optimal air-fuel ratio can vary depending on factors such as engine design, operating conditions, and fuel characteristics. However, for most spark ignition engines, including gasoline-powered vehicles, a mixture close to 12 parts air to 1 part fuel is commonly used for maximum power generation.