Answer:
1) Function
2)Function
3) Not a function
4) Function
Explanation:
The same process applies from the previous one, the x values can not repeat if it is a function.
For the first one the x values do not repeat only the y's. Therefore it is a function.
For the second one the x values do not repeat either, therefore it is a function.
For the third one the x values repeat multiple times making it not a function.
For the fourth one the x values do no repeat making it a function.