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Answer: Choice D</h3>
All vertical lines intersected the curve at exactly 1 point.
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Explanation:
If there is a case when a single vertical line crosses 2 or more points on the curve, then it will not be a function. In this situation, it is said that the curve fails the vertical line test.
Passing the vertical line test means that every vertical line passes through exactly one point on the curve. Each x input leads to exactly one output. If such a situation happens, then we have a function.
Since Kelly concluded that the curve is a function, this means the curve passed the vertical line test, and it points us to choice D as the answer.
