For any real number $x$, let $\tan^{-1}(x)$ denote the unique real number $\theta$ in $(-\pi/2, \pi/2)$ such that $\tan\theta = x$. Then $\lim_{n \to \infty} \sum_{m=1}^{n} \tan^{-1}\left\{\frac{1}{1+m+m^{2}}\right\}$
(a) Is equal to $\pi/2$
(b) Is equal to $\pi/4$
(c) Does not exist
(d) None of the above.