A wound-up watch spring possesses
A) Kinetic energy
B) Elastic potential energy
C) Nuclear energy
D) Sound energy

Hint: Elastic P.E. of a body is the energy possessed by the body due to its deformation in size. Elastic energy will get stored in the body if it is subjected to any elastic deformation through work done on it. Wounding up a spring changes its shape and size.

Complete Step By Step Solution:
Wounding-up a spring involves spiraling a spring or framing it into a more compact structure.
Kinetic energy of a body is the energy possessed by the body by virtue of its motion. Since every point of spring is at rest. The kinetic energy possessed by spring is zero.
Elastic potential energy of a body is the energy possessed by the body by virtue of its configuration. Since the configuration or shape of spring is changed during wounding, its P.E. is non-zero.
Nuclear energy is the energy released during nuclear reaction. Since our spring is not going through any nuclear reaction, the nuclear energy possessed by spring is zero.
Sound energy is the energy carried by sound waves. Our spring is not producing any sound. So the sound energy possessed by spring is zero.
Hence the correct option is B.

Note: The spring has some energy and can be verified by the fact that it exerts a force on an object from its ends. Thus it can do work. This energy must be coming from somewhere; this is the elastic P.E. which is stored in the spring.