Explanation

(c)
On comparing the given lines with
$y = m_{1}x + c_{1}\ and\ y = m_{2}x + c_{2},\ we\ get$
$m_{1} = 2\ and\ c_{1} = 7$
$and\ m_{2} = 2\ and\ c_{2} = 5$
$\therefore Required\ distance = \frac{\left| c_{1} - c_{2} \right|}{\sqrt{(m)^{2} + 1}}$
$= \frac{|7 - 5|}{\sqrt{{(2)}^{2} + 1}} = \frac{2}{\sqrt{5}}$