Which of the following relations is a function?
A {(1,2),(2,3),(3,4),(4,5)}
B {(1,2),(1,3),(2,4)}
C {(2,1),(3,1),(2,2)}
D {(0,0),(1,1),(0,2)}
Explanation
A function maps each input (x) to exactly one output (y). The first set has unique x-values, so it is a function. Others have repeated x-values.