(c)
Let $f(x) = \log\left( \frac{x - 1}{x + 1} \right)$
$f( - {x) = log}{\left( \frac{- x - 1}{- x + 1} \right) = - \log\left( \frac{x - 1}{x + 1} \right)}$
$= - f(x)$
$\Rightarrow f(x)$is an odd function
$\therefore\ \int_{- 1}^{1}{\log{\left( \frac{x - 1}{x + 1} \right)dx = 0}}$