How is fuel discharged at idling speeds in a float-type carburetor?

In a float-type carburetor, fuel is discharged at idling speeds primarily through the idling jet. This jet specifically regulates the fuel flow when the engine is running at low RPM and ensures the engine receives the appropriate mixture of fuel and air for smooth operation during idle conditions. The idling jet is designed to deliver a precise amount of fuel to maintain the necessary combustion in the engine at these low speeds, contributing to stability and efficiency in fuel consumption.

While the main jet, secondary jet, and economizer system serve critical roles at different operating conditions, they are not involved in the operation at idle speeds. The main jet is responsible for fuel delivery at higher RPMs when the throttle is open wider, while the secondary jet typically activates under specific conditions in multi-barrel carburetors for additional power. The economizer system functions to optimize fuel delivery during varying loads and throttle positions but is not operative during idle. Thus, the idling jet is the designated component for managing fuel flow at low speeds, making it the correct answer.