An interference pattern $($such as from a double slit experiment$)$ tells us what?

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that the thing being investigated $($light$,$ electrons$)$ has wave$-$particle duality

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that the thing being investigated $($light$,$ electrons$)$ behaves as a particle

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that the thing being investigated $($light$,$ electrons$)$ is a quantum object

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that the thing being investigated $($light$,$ electrons$)$ behaves as a wave