Solution:Surplus energy theory was proposed by Schiller 1873 and Spencer 1875.
Schiller suggested that play was essentially 'the aimless expenditure of surplus energy' i.e. play resulted from the superfluious energy that remained after the primary needs were satisfied.
Spencer extended the Schiller theory, adding the elements of imitation and a physiological explaination of play. He suggested that play is the simulation of activities of organism, when play, it is forced to exercise.