Which function is linear?

Responses
A f(x) = 5
+ 10f(x) = 5 x 2 + 10
B f(x) =

+ 10f(x) = 5 x + 10
C f(x) = 5
− 10f(x) = 5 x 2 − 10
D f(x) =

− 10

The linear function is:

B f(x) = 5x + 10