Explanation

(c)
$N = \frac{N_{1}V_{1} + N_{2}V_{2}}{V_{1} + V_{2}}$ $(\because for\ HCl\ N = M)$
$= \frac{0.015 \times 100 + 0.005 \times 100}{100 + 100}$
$= \frac{1.5 + 1.5}{200} = \frac{1}{100} = 10^{- 2}$
Resulting solution is acidic in nature.
Then, $\left\lbrack H^{+} \right\rbrack = 10^{- 2}$
$pH = - \log{\lbrack H^{+}\rbrack}$
$= {log\ }\frac{1}{\lbrack H^{+}\rbrack} = \log\frac{1}{10^{- 2}}$
$= 2\log{\ 10}$
$= 2\$