(c)
$\because y = \tan^{- 1}{\left( \frac{\log\left( \frac{e}{x^{2}} \right)}{\log{ex^{2}}} \right) + \tan^{- 1}\left( \frac{3 + 2\log x}{1 - 6\log x} \right)}$
$= \tan^{- 1}\left( \frac{1 - \log x^{2}}{1 + \log x^{2}} \right) + \tan^{- 1}\left( \frac{3 + 2\log x}{1 - 6\log x} \right)$
$= \tan^{- 1}{(1) - \tan^{- 1}{(2\log{x) + \tan^{- 1}{(3) + \tan^{- 1}{(2\log{x)}}}}}}$
$\therefore y = \tan^{- 1}{(1) + \tan^{- 1}{(3)}}$
$\Rightarrow \frac{dy}{dx} = 0\ \Rightarrow \ \frac{d^{2}y}{dx^{2}} = 0$