From the diagram above,
the image D was reflected
and that reflection was
reflection is reflection on the line
x =0 or reflection on the y-axis
From reflection on the y-axis
we use the expression
( x,y )____ ( -x, y ).
so when you check from the diagram, it's only image D which is in the negative x , positive y plane.
this means that image D was reflected on the line x=0
