I= $∫a^{5x+3}dx$ is:

$a^{5x+3}+C$, where C is a constant $\frac{a^{5x+3}}{5\, log_ea}+C,$ where C is a constant $\frac{a^{5x+3}}{5}+C,$ where C is a constant $\frac{a^{5x+3}}{log_ea}+C,$ where C is a constant

$\frac{a^{5x+3}}{5\, log_ea}+C,$ where C is a constant