Integrate : $\int x^5 \sec^2 (7x^6+9) dx$

Question

$(a)\;\frac{1}{42} \tan (7x^6 +9)+c \qquad(b)\;\frac{1}{42} \cot (7x^6 +9)+c \qquad(c)\;\frac{1}{42} \sin (7x^6 +9)+c \qquad (d)\;None$