Answer: B. x = 0
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Step-by-step explanation:
The table shows the inputs of -5, -1, x, 1 and 3. Ignore the x for now. The numerical inputs are -5, -1, 1, 3
If we have any input repeat itself with a different paired y value, then we will not have a function.
So if x = -5, then we don't have a function. This is because x = -5 is already paired with y = 4 in the top row. We can't have the input x = -5 lead to y = 0 at the same time. Any input must lead to exactly one output only. So this rules out choice A as a possible answer.
Choice C and choice D are eliminated for similar reasons as well. This leaves choice B. We don't have x = 0 yet, so it is a valid possible input. We can pick any thing we want for x as long as its not already done so in the table.