Choice A is the correct answer. Calculate using half-lives.

1. Half-lives: $\frac{32}{8} = 4$ half-lives.
2. Remaining: $200 \times (\frac{1}{2})^4 = 200 \times \frac{1}{16} = 12.5$ grams.
3. Formula: $A(t) = 200(0.5)^{t/8}$.

💡 Strategic Tip: 4 half-lives means $\frac{1}{16}$ of original remains.

Choice B is incorrect because this is after 3 half-lives (24 days). Choice C is incorrect because this would be after 5 half-lives (40 days). Choice D is incorrect because this is after 2 half-lives (16 days).