Answer:
Function A. <em>nonlinear</em>
Function B. <em>linear</em>
Step-by-step explanation:
Function A is nonlinear because the y values are changing at a nonlinear rate. To get from 0 to 1, the value is increased by 1. However, to get from 1 to 8, it increases by 7, which is different than before.
Function B is linear because the equation models a linear function. You can test this by drawing a table of values similar to Function A:

You can see the y values change at a linear rate of -1 constantly.