Question

force b in the image above represents...
buoyant force
normal force
magnetic force
air resistance

Explanation:

The normal force is a contact force that acts perpendicular to the surface of contact. In the image, the table exerts an upward - acting force on the backpack to support it, which is characteristic of the normal force. Buoyant force acts in fluids, magnetic force involves magnets, and air resistance acts on objects moving through air.

Answer:

normal force