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Explanation:
Direct variation equations are of the form y = kx
k = constant of variation
For choice A, we have k = 1 to lead to y = 1x or simply y = x.
This is why choice A is the answer.
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Choice B is ruled out because it's not linear.
Choice C is ruled out because the y intercept is not 0. All direct variation equations go through the origin.
Choice D is ruled out for the same reason as choice C.
