Answer:
A
(1,5),(2,6),(4,5)
Step-by-step explanation:
Think of the answer choice in a table
x | y
1 | 5
2 | 6
4 | 5
exactly one input (x) has one output (y)
in a function likw this you have to make sure that the x is going to one y.
if not than it is not a function.
(1,2),(1,5)(3,9)
see the one in this orderd pair goes to 2 and 5 so in is not a function