Answer: Choice B
The relation { (3,4), (-3, 8), (6,8) } is a function.
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Step-by-step explanation:
Choice A can be ruled out because we have x = -3 repeat itself for different y values. For any x input, there must be exactly one y output. This is assuming the x value is in the domain of course.
Choice C can be ruled out for similar reasoning. This time x = 3 repeats.
Choice D is the same story, but we go back to x = -3 showing up twice.
Choice B is the only thing left. Each x value is unique or only written one time. This graph passes the vertical line test. The other graphs fail the vertical line test (it is possible to draw a vertical line through more than one point).