Choice A is the correct answer. Solve for $t$ when $A(t) = 0.1(500) = 50$.

1. Equation: $50 = 500e^{-0.03t}$.
2. Divide: $0.1 = e^{-0.03t}$.
3. Take natural log: $\ln(0.1) = -0.03t$.
4. Solve: $t = \frac{\ln(0.1)}{-0.03} = \frac{-2.303}{-0.03} \approx 76.7 \approx 77$ years.

💡 Strategic Tip: When solving exponential decay, use natural logarithm to isolate $t$.

Choice B is incorrect because this is too short a time. Choice C is incorrect because this is slightly too long. Choice D is incorrect because this is about half the correct answer.