Which of the following represents a function?

  see below

Step-by-step explanation:

A graph is a function if any vertical line intersects points on the graph only once. The graph of A is a function.

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Ordered pairs represent a function if no x-value is repeated. In the list of B, the x-value -1 shows up twice. The list of B is not a function.

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As with ordered pairs, a table represents a function if no x-value is repeated. In the table of C, the x-value 3 shows up twice. The table of C is not a function.

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A mapping diagram represents a function if each x-value is only mapped to one y-value. In the map of D, the x-value 3 is mapped to two different y-values. The map of D is not a function.

just sum

10 + 10 = 20