Choice A is the correct answer. The asymptote comes from the vertical shift.

1. Form: $g(x) = ab^x + k$ where $k = -10$.
2. As $x \to \infty$: $(0.75)^x \to 0$, so $g(x) \to 0 - 10 = -10$.
3. Asymptote: $y = -10$.

💡 Strategic Tip: The constant term added/subtracted determines the horizontal asymptote.

Choice B is incorrect because 80 is the coefficient, not the asymptote. Choice C is incorrect because 0.75 is the base. Choice D is incorrect because this ignores the $-10$ shift.