These tables of values represent functions. In which table do the values represent and exponential function?

A. X Y
1 5
2 9
3 13
4 17
5 21

B. X Y
1 12
2 13
3 14
4 15
5 16

C. X Y
1 16
2 29
3 42
4 55
5 68

D. X Y
1 5
2 10
3 30
4 40
5 80