Answer:
The relationship is not a function.
Step-by-step explanation:
A relation is a function if and only if for each value of the variable x there exists a single value of f(x).
This means that if for a single value of x there is more than one value of y then the relation is not a function.
For the case shown in the image we have two variables.
The variable Months on the axis of abscissas and the variable days on the axis of the ordinates.
Note that for the month of February there are 2 different values of number of days, 29 and 28. Therefore, the relationship is not a function.