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Answer:
functions: A, C; non-functions: B, D
Explanation:
A relation is not a function if any input value (x) maps to more than one output value (y).
On a graph, we apply the "vertical line test." If any vertical line intersects two or more points on the graph, it is not a function. We say it fails the vertical line test. The bottom graph (D) fails the vertical line test, so is not a function.
On a mapping, such as figure B or C, any input (x-value) that is the source of two or more arrows means the relation is not a function. The map of B is not a function.
The other choices (A and C) show a functional relation.