Answer:
See below.
Explanation:
Graph A is a function because it passes the vertical line test. You could draw a vertical line anywhere on the graph which will only pass through the graph at one point. It is a many-to-one relation.
Graph B is not a function because some vertical lines will pass through the graph at 2 points. It is a one-to-many relation.,
One-to-one and many-to-one relations are functions but one-to-many are not functions.