What is thermal energy?

the distance between particles and their freedom to move around
a material that is a conductor of heat
the measurement of energy in an object due to position, conduction, or chemical composition
the total kinetic energy of all particles in a substance

The total kinetic energy of all particles in a substance is the correct answer. Thermal energy refers to the internal energy of an object or substance due to the motion of its particles. It is directly related to the temperature of the object or substance.