Answer:
Yes
Explanation:
A function correlates elements from a set one and only one element from a different set. Think of a train timetable: you can't have the same train in two points at a given time.
An easy way to solve the problem is to take a ruler (or the edge of a sheet of paper, as long as it's straight) and scan the graph parallel to the Y axis. As long as you don't touch the graph more than once, it's a function (zero points is ok!)