(c)
Line making equal intercepts therefore, its equation is
$x \pm y = a$ …(i)
Since, it passes through (2, 4)
$\therefore\ \ a = - 2,\ 6$
Hence, equation of the required lines are
$x \pm y = a$
$\Rightarrow x + y = - 2$
or $x + y = 6$
$\Rightarrow \ x + y - 6 = 0$