Where do reactions in a solid generally take place? A. At the center of the solid.
B. All throughout the solid
C. Only on opposite sides of the solid due to repelling forces.
D. On the surface of the solid.

It's D.  On the surface of the solid.

Explanation:

If the reactant is a solid, the surface area of the solid will impact how fast the reaction goes. This is because the two types of molecule can only bump into each other at the liquid solid interface, i.e. on the surface of the solid. So the larger the surface area of the solid, the faster the reaction will be.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds