Answer:
Top graph only
Step-by-step explanation:
A function links two set in a way that for each element from the origin set (called domain) you get one and only one element of the target set (co-domain, or range). In layman terms, once you pick your x, you get a single y. In term of graphing it it means that a vertical line of equation touches the function either zero times (c is outside the domain, or only once (if c is in the domain. If you try it on the various functions there are intervals where you are touching the graphs twice. Or even infinite times as it happens in the last one.
