Answer:
The first possible answer, -27a³b^6 + 8a^9b^12, is the sum of cubes.
Explanation:
The middle two possible answers involve " a " with no exponent, so these could not be correct.
Looking at the first and fourth possible answers, we see that the first term of -27a3b6+8a9b12 is a perfect cube; it could be re-written as (-3ab²)³. The second term could be rewritten as (2a³b^4)³. So the first possible ansswer is the SUM of CUBES.