Let A = {1, 2} and let B = {2, 3, 4}. Which of the following shows B ∆ A? A) {3, 4}
B) {1, 3, 4}
C) {(1,2), (1,3), (1,4), (2,2), (2,3), (2,4)}
D) {(2,1), (2,2), (3,1), (3,2), (4,1), (4,2)}