Answer: B
Number on the left: x-value
Number on the right: y-value
If there are 2 y-values for one x-value it is NOT considered a function.
For instance in the answer:
(2,3), (2,4), (3,3), (3,4)
You can clearly see that the x-values (2 & 3) repeat more than once; therefore, it is NOT a function.
On the other hand if you have 2 DIFFERENT x-values for the same y-value it IS A FUNCTION.
For ex D: (2,4), (3,4), (5,4), (6,4)
As you can see there are 4 DIFFERENT x-values with same y-value; therefore it is A FUNCTION
To make it easier:
If x-values appear more than once = NOT A FUNCTION
If x-values appear only ONCE = FUNCTION
Remember: y-values are ALLOWED to repeat
I hope this helps. If you have any questions please let me know in the comments.
