(d)
$\int_{}^{}\frac{1}{\sin^{2}{x.\cos^{2}x}}\ dx = \int_{}^{}\frac{\sin^{2}x + \cos^{2}x}{\sin^{2}{x\cos^{2}x}}\ dx$
$= \int_{}^{}\left( \frac{1}{\cos^{2}x} + \frac{1}{\sin^{2}x} \right)dx$
$= \int_{}^{}{(\sec^{2}{x + cosec^{2}\ x)}}dx$
$= \tan x - \cot x + c$