The answer is A.
When simplifying radicals, you can factor out anything that is a root. In this case we have a 4th root. We can break 144 to 16*9. By doing this, we can pull out 16 which has the 4th root 2 (2*2*2*2=16). Next, a^12 has the 4th root a^3. We can't do anything with the b^3 so it stays inside the root with the 9.
