Evaluate the integral:

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{1}{x^2\sqrt[\phantom{2}]{x^2+4}}dx$

Select one:

$a.-\frac{1}{4}*\frac{x}{\sqrt[\phantom{2}]{x^2+4}}+C$

$b.-\frac{1}{4}*\frac{\sqrt[\phantom{2}]{x^2+4}}{x}+C$

$c.\frac{1}{4}*\frac{x}{\sqrt[\phantom{2}]{x^2+4}}+C$

$d.\frac{1}{4}*\frac{\sqrt[\phantom{2}]{x^2+4}}{x}+C$