If $p=\cos 55^{\large\circ},q=\cos 65^{\large\circ}$ and $r=\cos 175^{\large\circ}$ then the value of $\large\frac{1}{p}+\frac{1}{q}+\frac{r}{pq}$ is

Question

$(a)\;0\qquad(b)\;-1\qquad(c)\;1\qquad(d)\;None\;of\;these$