Choice A is the correct answer. Analyze the function form.

1. Form: $y = ab^x + k$ where $k = -2$.
2. Asymptote: As $x \to \infty$, $(0.9)^x \to 0$, so $y \to 0 - 2 = -2$.
3. Conclusion: Horizontal asymptote is $y = -2$.

💡 Strategic Tip: The vertical shift $k$ determines the asymptote.

Choice B is incorrect because 7 is the coefficient, not the asymptote. Choice C is incorrect because$b < 1$ means decreasing (decay). Choice D is incorrect because y-intercept is $7(1) - 2 = 5$, at $(0, 5)$.