if a 1 3 4 8 and b 3 5 7 find a u b

If A = {1, 3, 4, 8} and B = {3, 5, 7}, find A U B. A. {1, 3, 3, 4, 5, 7, 8} B. {1, 3, 4, 5, 7, 8} C. {1, 4, 5, 7, 8} D. {3}