When a Single Boxcar in the Freight Yard Hooks onto a Stationary

Multiple Choice

When a single boxcar in the freight yard hooks onto a stationary string of four boxcars, as in example 7.4, there is some kinetic energy lost. Which of the following could account for the missing energy?

A) Sound energy in the loud CLANG when they hook together.
B) Heat energy in the clamping mechanism between cars as it opens and then captures the fifth boxcar.
C) Both A and B