The capability to do work is said to be energy. It can neither be created nor be destroyed according to law of conservation of energy. Energy exist in different forms depends upon the work to be done such as potential energy, kinetic energy, mechanical energy, heat energy etc.
Now, when the guitarist plucks the guitar strings to make sound, he uses mechanical energy and when guitarist plucks the guitar strings guitar produces sound energy also.
Thus, option (d) is the correct answer.