Which of the following sets represents the domain of the function shown? {(2, 7}, (15, 13), (21, –4), (24, 18)} A) {-4,2,7,13,15,18,21,24} B) {7,2),(13, 15),(-4,21),(18,24) C) {2,15,21,24} D) {-4,7,13,18}