Answer:
The second table, the table in the middle.
Explanation:
Since the x-values of all the tables differ by 1, the difference between the y-values must be constant in order for the table to be linear. In second table, the different between the first and second y-value (from top to bottom) is 3, however the difference between the second and third and third and fourth values are 1.5, which is not constant. Therefore, the second table is nonlinear.