Explanation

(c)
Let equation of line parallel to $3x - y = 7$ be $3x - y = \lambda$.
The passes through (1, 2)
$\therefore\ 3 - 2 = \lambda\ \Rightarrow \ \lambda = 1$
$\therefore\$Line is $3x - y = 1$
The point of intersection of $x + y + 5 = 0$ and $3x - y = 1$ is $( - 1,\ - 4)$
$\therefore$ Distance between (1, 2) and $( - 1,\ - 4)$
$= \sqrt{(2)^{2} + (6)^{2}} = \sqrt{40}$