Answer
The function is linear.
Slope $= 4$
Work Step by Step
A function is linear if there is a constant rate of change of the function, which is also called the slope.
Note that:
$0=-4+4\\
4=0+4\\
8=4+4\\
12=8+4$
Hence. the difference of all consecutive $y$-values is $4$, which means that the slope is $4$.
Thus, the function is linear.