Following the proper u-substitution, which of the following integrals can we use to solve ∫ tan⁹xsec²x dx ?
a. ∫ u⁷ + u² du
b. ∫ u⁸ du
c. ∫ u⁹ du
d. ∫ u¹⁰ - u du
e. ∫ u¹¹(u²-1)² du