Choice Bhoice D is the correct answer.

1. Define: Time B = $t$, Time A = $t + 2$.
2. Distance Equal: $6t = 3(t + 2)$
3. Simplify: $6t = 3t + 6$
4. Subtract 3t: $3t = 6$
5. Divide by 3: $t = 2$
6. Verify: $12 = 3(4) = 12$ ✓

Choice Bhoice D is incorrect because calculation error.

Choice Bhoice A is incorrect because calculation error.

Choice Bhoice C is incorrect because calculation error.