Tích phân $I=\int\limits_{{-\frac{\pi }{3}}}^{{\frac{\pi }{3}}}{{\frac{{x\sin x}}{{{{{\cos }}^{2}}x}}dx}}$ bằng?
A. $\frac{{4\pi }}{3}+\ln \frac{{2-\sqrt{3}}}{{2+\sqrt{3}}}.$
B. $\frac{{4\pi }}{3}-\ln \frac{{2-\sqrt{3}}}{{2+\sqrt{3}}}.$
C. $\frac{1}{2}\ln \frac{{2+\sqrt{3}}}{{2-\sqrt{3}}}.$
D. $-\frac{1}{2}\ln \frac{{2+\sqrt{3}}}{{2-\sqrt{3}}}.$