Explanation

(d) Gravitational potential energy is given as
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ U = - \frac{GMm}{r}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ U_{1} = - \frac{GMm}{r_{1}},U_{2} = - \frac{GMm}{r_{2}}$
$As\ r_{2} > r_{1},\ hence,$
$\ \ \ \ \ \ \ \ \ \ \ U_{1} - U_{2} = GMm\left\lbrack \frac{r_{2} - r_{1}}{r_{1}r_{2}} \right\rbrack\ is\ positie$
$ie,\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ U_{1} > U_{2}$
$or\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ U_{2} < U_{1}$
$ie,$ gravitational potential energy increases.