Answer:
a. y=-2x
Step-by-step explanation:
The equation of a direct proportion is of the form [tex]y=kx[/tex] where k is the constant of proportionality.
From the given options, the only equation that is of the form, [tex]y=kx[/tex] is
[tex]y=-2x[/tex].
In this case [tex]k=-2[/tex] is the constant of proportionality.
Therefore the correct option is A.
