The equation of a parabola is $(y-k)^{2}=4 a(x-h)$ where, $a>0$. The vertex and focus are respectively at
(a) $(\mathrm{h}, \mathrm{k})$ and $(\mathrm{a}, \mathrm{k})$
(b) $(\mathrm{h}+\mathrm{a}, \mathrm{k}+\mathrm{a})$ and $(\mathrm{h}, \mathrm{k})$
(c) $(\mathrm{h}, \mathrm{k})$ and $(\mathrm{h}-\mathrm{a}, \mathrm{k})$
(d) $(\mathrm{h}, \mathrm{k})$ and $(\mathrm{h}+\mathrm{a}, \mathrm{k})$