What are the forces of nature that creates electromagnetism

The potential in a region between x = 0 and x = 6.00 m is v = a + bx, where a = 14.0 v and b = -7.30 v/m.

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity