Choice A is the correct answer. We are given $d = 64$ and need to find $t$.

1. Substitute $d=64$: $64 = 16t^2$.
2. Divide by 16: $4 = t^2$.
3. Take the square root: $t = \pm 2$.

Since time cannot be negative, $t = 2$ seconds.

Choice B is incorrect because $16(4)^2 = 256$. Choice C is incorrect because $16(8)^2 = 1024$. Choice D is incorrect because it solved linearly $16t = 64$.