In the Reduce phase of a MapReduce computation, each reducer gets $($as input$)$ a list of Value$2$ objects, along with a key $"$k$"$ of type Key$2.$ What is the best description of what this list consists of$?$

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These are the Value$2$ objects that the Shuffle phase of the MapReduce operation happened to randomly assign to this particular reducer.

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These are the objects that were input to the Map phase of the computation, but were not output from the user$-$supplied "map" function.

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These are the Value$2$ objects that are output from the user$-$supplied "reduce" function in the Reduce phase of the computation.

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These are all of the Value$2$ objects that were assigned the key $"$k$"$ during the Map phase of the MapReduce.