Which set of ordered pairs represents a function? A {(2, 7), (2, 8), (3, 8)}
B {(3, 2), (3, 3), (3, 4)}
C {(4, 1), (5, 1), (4,4)}
D {(5, 6), (8, 6), (9, 6)}
does anyone know the answer

Abicycle training wheel has a radius of 3 inches. the bicycle wheel has a radius of 10 inches.approximately how much smaller, in square inches and rounded to the nearest hundredth, is the area of the training wheel than the area of the regular wheel? *