If A is the set of even integers less than 10, and B is the set of multiples of 3 less than 20, what is the union of sets A and B? (A) {2, 4, 6, 8} (B) {3, 6, 9, 12, 15, 18} (C){6} D) {2, 3, 4, 6, 8, 9, 12, 15, 18} (E) {2, 4, 6, 8, 10, 12, 14, 16, 18}