What is quantum physics? ​

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.

Determine the maximum r-value of the polar equation r =3+3 cos 0

Awave is produced in a rope. the wave has a speed of 33 m/s and a frequency of 22 hz.