Which of the following components is closest to the fuselage on the wing?

The component that is closest to the fuselage on the wing is the flap. Flaps are located on the trailing edge of the wing and extend inward towards the fuselage. They play a crucial role in enhancing lift during take-off and landing by increasing the wing's surface area and changing its shape, which enables the aircraft to fly safely at lower speeds.

In contrast, ailerons, which are also located on the trailing edge but further out on the wing, are primarily used for roll control. The leading edge is the front edge of the wing, while slats, which are additional lift-enhancing structures, are fitted forward of the main wing structure and also closer to the leading edge but not as close to the fuselage as the flaps. Thus, flaps, being adjacent to the fuselage and performing important functions for flight dynamics, are the correct answer in this context.