Quadrilateral abcd underwent a sequence of transformations to give quadrilateral a′b′c′d′. which transformations could have taken place?
a) a reflection across the x-axis followed by a reflection across the y-axis
b) a translation 10 units down followed by a translation 8 units to the right
c) a rotation 90° counterclockwise about the origin followed by a reflection across the y-axis
d) a reflection across the line y = x followed by a reflection across the line y = -x