I just need the answer without explanation ASAP

Let f: X rightarrow Y be a function that maps elements of a set X (domain) to those of a set Y (target). Which of the following statements is possibly false? The range of f is a subset of Y. For every y elementof Y, there is a unique x elementof X such that f(x) = y. The set {(x, y)|x elementof X, and f(x) = y} is a subset of X times Y. For every x elementof X, there is a unique y elementof Y such that f(x) = y