Answer: Option A: a taut guitar string
Step-by-step explanation:
The sum total of kinetic energy and potential energy is known as mechanical energy. The energy possessed by a body due to virtue of its position is known as mechanical potential energy. The energy possessed by a body due to virtue of its motion is known as motion is known as kinetic energy.
A taut guitar string possesses only mechanical potential energy.
The rest of the examples have either kinetic energy or combination of potential energy plus kinetic energy.
Hence, option A is correct.