Answer:
The correct option is 4.
Step-by-step explanation:
A relation is called a function if there exist a unique value of y for each value of x.
If means if a relation is defined as (x,y), then for each value of x there exist a unique value of y.
In option 1, at x=1, the values of y are 2 and 5.
Since there exist more than one values of y for a single value of x, therefore option 1 is incorrect.
In option 2, at x=1, the values of y are 2, 3, 4 and 5.
Since there exist more than one values of y for a single value of x, therefore option 2 is incorrect.
In option 3, at x=2, the values of y are 3 and 5.
Since there exist more than one values of y for a single value of x, therefore option 3 is incorrect.
In option 4, for each value of x, there exist single value of y, therefore option 4 is correct.
