A table is said to form a linear function if the ratio of change in input to output is same through out the table.
In the first table is not same through out. So, it is ruled out.
The change in input () is 3 and the change in output () is 4.
In the third and fourth tables is not same through out. So, they are ruled out.
Therefore,among the choices, table-2 forms a linear function.
Correct Answer is : Table 2