Direct variation is a relationship between two variables in which one is a constant multiple of the other. In particular, when one variable changes the other changes in proportion to the first. If b is directly proportional to a, the equation is of the form b = ka (where k is a constant).
Given the equation [tex]2x-4y=0,[/tex] you can see that
[tex]4y=2x,\\\\y=\dfrac{2}{4}x=\dfrac{1}{2}x.[/tex]
Then the constant [tex]k=\dfrac{1}{2}.[/tex]
Answer: correct choice is C.
