Which of the following is a nonlinear function?

a.
input
1
2
3
4
5
output
4
12
20
28
36

b.
input
1
2
3
4
5
output
4
16
64
256
1,024

c.
input
1
2
3
4
5
output
4
10
16
22
28

d.
input
1
2
3
4
5
output
4
8
12
16
20