Answer:
The second set of ordered pairs : 
{(3,-1),(7,1),(-6,-1),(9,1),(2,-1)}
Step-by-step explanation:
A function in IR2 (coordinate plane) assigns to a value of ''x'' an unique value of ''y''.
For example, the function  .
.
When  ⇒
 ⇒ 
Therefore, the ordered pair  belongs to the function.
 belongs to the function. 
For each value of ''x'' we will have an unique value of ''y''. 
For example, the ordered pairs  and
 and  don't belong to any function because the value ''4'' can't be assign to ''5'' and ''8'' at the same time.
 don't belong to any function because the value ''4'' can't be assign to ''5'' and ''8'' at the same time. 
On the other hand, we can have the same value of ''y'' assigns to different values of ''x''. For example ,  and
 and  are correct ordered pairs for the function
 are correct ordered pairs for the function  .
.
In order to answer the question, we will discard the sets in which two or more ordered pairs have the same value of ''x'' assign to a different value of ''y''. 
Examining the sets we find that the first set has the ordered pairs  and
 and  so it is not a valid set of ordered pairs which represents a function.
 so it is not a valid set of ordered pairs which represents a function. 
The second set is correct.
The third set has  and
 and  so it doesn't represent a function.
 so it doesn't represent a function.
We will have the same problem in the fourth set with the ordered pairs  ,
 ,  and
 and  .
.
The only correct set is the second one.