which of the tables below doesn’t represent a function?

table a
x y
5 1
2 4
3 6
0 6
table b
x y
7 7
6 3
0 4
9 0
table c
x y
5 7
9 2
1 5
5 5

The table that doesn't represent a function is table c. This is because the x-value of 5 is associated with multiple y-values (7 and 5). In a function, each x-value should have only one corresponding y-value.