Answer:
2nd choice. -a^3 - 8ab^2
Explanation:
(3a^3b - 4ab^2 + 5ab) - (4a^3b + 4ab^2 + 5ab)
Distribute the minus sign and take out the parenthesis.
3a^3b - 4ab^2 + 5ab - 4a^3b - 4ab^2 - 5ab
Combine like terms.
3a^3b - 4ab^2 -4ab^2 - 4ab^2 + 5ab - 5ab
-1a^3b - 8ab^2