Which relationship is a function?

Answer: The first relationship is a function.
Step-by-step explanation:
A relation is said to be a function if for each input value ( independent variable) there exist only one unique output value ( dependent variable).
Here teachers are denoted as independent variable
Mrs. Valverde has two pets , i.e. there are two output values corresponds to one input value, hence it is not a function., so by definitin
After observing all of the options , we can say that , the correct option is first one.
i.e. The first relationship is a function.