Which transformation can be applied to the blue figure to create the red figure?

a: reflection across the y-axis, and then rotation 90 counterclockwise around the origin
b: rotation 180° around the origin, and then reflection across the y-axis
c: rotation 90° clockwise around the origin, and then reflection across the x-axis
d: reflection across the line y=x, and then rotation 90° counterclockwise around the origin