Answer:
A. y=0
Explanation:
This is the equation because y=0 is just a horizontal line across the x-axis, so it'll be perpendicular with AB and go through (0,0).
y=x is wrong because it starts at the origin and goes up with positive slope of 1.
x=0 is just the y-axis, also wrong.
y=1 is just a horizontal line at one, so it's perpendicular to AB, but it doesn't go through the origin.
Hope this helps!