It's probably too late, but just in case:
Work is done by the student as energy is transferred from the chemical store in their muscles to the kinetic and gravitational potential energy stores of the trolley. However, not all energy will be converted to GPE, as there will be some dissipation of energy as a result of friction between the trolley and the ramp. This will increase the temperature of the surroundings.
(Physics was always my worst science, someone correct me if I'm wrong). Hope this helps xx