The two reasons the length of the toy car's front end changes more when the car's speed is greater are:
C. A faster toy car has greater kinetic energy, so the front end needs to absorb more energy.
A. A faster toy car needs a greater unbalanced stopping force to stop somewhat instantly.
While option B discusses friction, it doesn't directly relate to the length change due to speed as clearly as options A and C do. Option D also doesn't directly pertain to the observed change in length because potential energy is not the primary factor in the context provided.