Answer: B) 1
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Step-by-step explanation:
I'm assuming you were given the list of points to be
{(2,8). (12,3).(c,4), (-1,8). (0,3}}
the x coordinates of each point are: 2, 12, c, -1 and 0
If c is equal to any of the other x coordinates (2, 12, -1, or 0), then this will mean we have a repeated x coordinate. In turn, this leads to us not having a function.
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Consider the case that c = 2.
This means that (2,8) and (2,4) are two points in this relation. The input x = 2 leads to multiple outputs y = 8 and y = 4 at the same time. A function is not possible here. A function is only possible if we have any given input lead to exactly one output only. So this is why c = 2 is not possible if we want a function. The same goes for the other x coordinates mentioned.
All of this means we can rule out choices A, C, and D
Choice B means that c = 1 and this x coordinate hasn't been mentioned yet. So this could be a value of c that leads to a function. This is why choice B is the final answer.