Correct Answer - A
When the man climbs the ladder of length l, the balloon descends by height h. So net height gained by the man is `l-h`. Hence, gain in potential energy of the man is `mg(l-h)`.
Work done by man: `W_1=mgl`
Inclination in potential energy of balloon=work done by man -increase in potential energy of man, i.e.,
`mgl-mg(l-h)=mgh`