(A + B')(C' + D). Given Boolean function: A'B + CD' + A'B + CD' First simplify the given expression: A'B + A'B = A'B (redundant term) CD' + CD' = CD' (redundant term) So, the simplified function = A'B + CD' Now, we are asked to find the complement of this function: Let F = A'B + CD' Then the complement is: F' = (A'B + CD')' Apply De Morgans Law: (A'B + CD')' = (A'B)' · (CD')' (A'B)' = A + B' (CD')' = C' + D Therefore, F' = (A + B')(C' + D) Hence, the correct answer is:Option 3) (A + B')(C' + D)