Final answer:
The work function denotes the amount of energy required to release an electron from a material, and it pertains to the energy subtracted to overcome the binding energy rather than adding to its kinetic energy. Therefore, the correct answer to whether the work function adds or subtracts kinetic energy is B) Subtracts.
Step-by-step explanation:
The work function refers to the minimum amount of energy that must be supplied to an electron to free it from the surface of a material. When it comes to work and energy in the context of physics, the principle to consider is the Work-Energy Theorem. This theorem states that the work done on an object increases its kinetic energy if the work is positive, or it decreases the object's kinetic energy if the work is negative.
Therefore, the correct answer to whether the work function adds or subtracts kinetic energy is B) Subtracts, as it represents the energy that must be overcome for the electron to escape, thus reducing its residual kinetic energy once it is free from the material.