Which sequence of rigid transformations will not map the preimage δabc onto the image δa′b′c′ ?
a. a reflection across the y-axis followed by a reflection across the x-axis
b. a rotation 90° clockwise about the origin followed by a reflection across the x-axis
c. a rotation 180° clockwise about the origin followed by a reflection across the line y = -x
d. a reflection across the line y = x