What do accessory gearboxes provide in relation to the main gearbox?

Accessory gearboxes serve a vital role in the overall functionality of an aircraft's engine system by mounting and driving essential components. These components can include fuel pumps, generators, and oil pumps, which are critical for the operation and performance of the engines. The accessory gearboxes transmit power from the main gearbox, facilitating the operation of these essential systems that support engine performance and overall aircraft operation.

This is foundational because the efficient functioning of these components directly affects the aircraft's operational capabilities. For instance, fuel pumps are crucial for delivering fuel from the fuel tanks to the engines, while generators provide electrical power necessary for various onboard systems. Each of these components relies on the accessory gearbox for its operation; thus, it is clear why this choice is the correct answer. The other options, while related to aircraft systems, do not accurately describe the specific function that accessory gearboxes fulfill in relation to the main gearbox.