Correct Answer - D
Using work - energy theorem, `W_("total") = Delta K`
i.e., woek done by gravity should be equal to change in the kinetic energy of the particle.
`W_("gravity") = (k_(f"inal") - K_("initial"))`
`W_("gravity") = (0 - (1)/(2) xx ((100)/(1000))(5)^(2)) = - 1.25 J`
Work done by force of gravity `= - 1.25 J`.