Answer:
The second one
Explanation:
In a function an input has a distinct output, so if I put 3 into a function and got 8, that is my answer and nothing else, if I put 3 again and get -2 then it isn't a function because I got a different answer. In the 1st, 3rd and 4th one there are two outputs for the same input so they aren't functions.
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