Question 2, Answer A

Right!

The car comes to a stop, so it loses kinetic energy.
There is work done on the car by only one external force, namely, kinetic friction (as it slides; negative work). To the extent that the work done by friction can be written as the product of the force times the displacement of the car's center of mass, it will also equal the change in the car's kinetic energy (by Eq. (7.12))
In addition to this, thermal energy is generated by friction. However, the amount of thermal energy gained by the car is not equal to the kinetic energy it loses, since the roadway also must warm up significantly in this case.
Note that this is an example of a system that is not closed: dissipation happens at the system's boundary (the point of contact between the car and the road). Hence, the result (7.20), W_{ext, sys} = Δ E_sys, does not apply.

Now answer this: if we chose the system to include the roadway, what would the work-energy diagram look like? Choose from the pictures shown below.