If the tangents at the two points $x=p$ and $x=q$ to the curve $y=(x-p)(x-q)(x-r)$ are parallel to one another then
(a) $\mathrm{p}, \mathrm{q}, \mathrm{r}$ are in $\mathrm{GP}$
(b) $\mathrm{q}, \mathrm{p}, \mathrm{r}$ are in $\mathrm{AP}$
(c) $\mathrm{r}, \mathrm{q}, \mathrm{p}$ are in $\mathrm{AP}$
(d) $\mathrm{p}, \mathrm{r}, \mathrm{q}$ are in $\mathrm{AP}$