Final answer:
A diesel combustion chamber with a single chamber fitted with an extra air valve allows for better control of the air-to-fuel ratio and more efficient combustion.
Step-by-step explanation:
The student is referring to a(n) diesel combustion chamber with a single chamber fitted with an extra air valve. This type of chamber allows for better control of the air-to-fuel ratio, resulting in more efficient combustion. The extra air valve allows additional air to be drawn into the chamber, ensuring complete combustion of the fuel.