In functions, two x's cant exist. It will create an undefined (straight down) line.
To figure out if there it is a function or not from a graph, do the pencil test. Take your pencil (or finger) and drag it across the graph vertically. If your pencil hits two points at once (on the same x-axis, or straight up/down), its not a function.
Therefore, both tables are not a function, or B.