\text { The derivative of the function } f(x)=\tan \left(x^{7}+9\right) \text { is: } \text { A) } f^{\prime}(x)=7 \mathrm{x}^{6} \sec ^{2}\left(x^{7}+9\right) \text { B) } f^{\prime}(x)=\sec ^{2}\left(x^{7}+9\right) \text {

D) None of them } \text { C) } f^{\prime}(x)=\sec \left(x^{7}+9\right) \tan \left(x^{7}+9\right)