Answer:
W only
Step-by-step explanation:
A function outputs for every point in the domain (horizontal axis or part of it) one and only one value of y. The easiest way to find out which one is a function is to grab a pen, or a ruler, or the edge of a piece of paper, put it parallel to the y axis, and scan the graph. if you touch your graph more than once (zero is still fine! means the function doesn't exist there) you're not dealing with a function.
