Final answer:
Elastic potential energy is the term that describes energy stored within a stretched object, such as a spring when it is deformed from its equilibrium position. Hence, the correct option is (A).
Step-by-step explanation:
The term that describes energy stored within a stretched object is A. Elastic potential energy. This type of potential energy is stored as a result of the deformation of an elastic object, such as the stretching of a spring. For a system that can be described by Hooke's law, the elastic potential energy (PEel) is given by the equation PEel = (1/2)kx², where 'k' is the force constant and 'x' is the displacement from the equilibrium position.
Kinetic energy is also referred to as the energy of motion, but it does not apply to a stretched object at rest. Gravitational potential energy pertains to an object's position above the Earth's surface or within a gravitational field and is not directly related to an object being stretched. Lastly, Thermal energy is the internal energy of an object due to its temperature, which again, is not specifically about the energy within a stretched object.