Which of the following relations are functions? . f = {(2,3), (1,2), (4,7), (6,9)} . g = {(2,9), (3,11), (5,13), (3,15)} h = {(5,9), (10,7), (11,12), (5,8)} f = {(1,0),(1,0),(2,3),(2,4)} ​