Tìm nguyên hàm
$\int{{\frac{{\sin x}}{{{{{\cos }}^{4}}x}}dx}}.$
A. $\frac{{-1}}{{3c\text{o}{{\text{s}}^{3}}x}}+C.$   
B. $\frac{1}{{3c\text{o}{{\text{s}}^{3}}x}}+C.$   
C. $\frac{1}{{\text{3si}{{\text{n}}^{3}}x}}+C.$  
D. $-\frac{1}{{\text{3si}{{\text{n}}^{3}}x}}+C.$

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