How to keep a portion of your brain alert while sleeping

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.

Science and technology are interdependent. advances in one lead to advances in the other. give an example of this phenomenon.

What’s #16 asking and how do i solve it?