1. The problem asks: Which graph represents a function? 2. Recall the definition of a function: For each input $x$, there must be exactly one output $y$. 3. This means that in the graph, no vertical line should intersect the graph at more than one point (Vertical Line Test). 4. Analyze each graph: - First graph: Points descend diagonally, each $x$ has one $y$. Passes the vertical line test. - Second graph: Similar to the first, each $x$ has one $y$. Passes the vertical line test. - Third graph: Points form a vertical line, multiple $y$ values for the same $x$. Fails the vertical line test. - Fourth graph: Multiple points share the same $x$ but different $y$ values. Fails the vertical line test. 5. Therefore, the first and second graphs represent functions, but since the question asks for which graph (singular), the first graph is a clear example. Final answer: The first graph represents a function.