Tìm nguyên hàm
$\displaystyle \int{{\frac{{{{{\cos }}^{2}}x}}{{{{{\sin }}^{4}}x}}}}dx.$
A. $\displaystyle -\frac{1}{3}{{\cot }^{3}}x+C.$
B. $\displaystyle \frac{1}{3}{{\cot }^{3}}x+C.$
C. $\displaystyle \frac{{5{{{\cos }}^{3}}x}}{{3{{{\sin }}^{5}}x}}+C.$
D. $A,B,C\begin{array}{*{20}{c}} {} & {sai.} \end{array}$