Explanation

(d)
Total number of socks = 5+4 = 9
The number of ways to select 2 socks out of 9 $= {\ ^{9}C}_{2}$
Number of ways to select both brown socks $= {\ ^{5}C}_{2}$
And number of ways to select both white socks $= {\ ^{4}C}_{2}$
$\therefore P$(Either both brown or white) $= \frac{{\ ^{5}C}_{2} + {\ ^{4}C}_{2}}{{\ ^{9}C}_{2}}$
$= \frac{\frac{5!}{3! \bullet 2!} + \frac{4!}{2! \bullet 2!}}{\frac{9!}{7! \bullet 2!}} = \frac{10 + 6}{36}$
$= \frac{16}{36} \times \frac{3}{3} = \frac{48}{108}$