Question

which graph shows a function?

Explanation:

Step1: Recall vertical line test rule

A graph represents a function if any vertical line drawn intersects the graph at most once.

Step2: Test top-left graph

Any vertical line intersects this parabola at most 1 point.

Step3: Test top-right graph

A vertical line (e.g., $x=5$) intersects 2 points, so not a function.

Step4: Test bottom-left graph

A vertical line (the y-axis, $x=0$) intersects infinitely many points, so not a function.

Step5: Test bottom-right graph

A vertical line (e.g., $x=2$) intersects 2 points, so not a function.

Answer:

The top-left graph (the downward-opening parabola) is a function.