Analysis: the mechanical energy lost by object B is divided into two parts: the kinetic energy of object A+the heat generated by friction (equal to the mechanical energy lost by the system, equal to the internal energy increase in the system).

Option B is wrong, because part of the work done by customer friction in B is converted into kinetic energy in A, not all of it is internal energy.

C is also wrong, just like option B.

The absolute value of the algebraic sum of the work done by D friction on object B and the work done on plate A should be equal to the increase of internal energy in the system, but not greater than.

I hope it helps you.