Final answer:
Gravity is the force that affects the normal forces as it determines the magnitude of the support force exerted by surfaces to prevent penetration. Option a) Gravity is the correct answer to which force affects the normal forces.
Step-by-step explanation:
In the given scenario of a b3-qrt68 stacked blocks, the force that affects the normal forces is gravity. This is because the normal force is a support force that surfaces exert to prevent solid objects from penetrating them. It acts perpendicular to the surface contact and is directly influenced by the gravitational force acting downwards on the body. In contrast, friction is a force that opposes the motion of two surfaces sliding against each other, tension relates to forces exerted by ropes or strings, and spring force is the restoring force exerted by a compressed or stretched spring. Option a) Gravity is the correct answer to which force affects the normal forces.