Which sequence of transformations produces an image that is not congruent to the original figure?

a. a translation of 3 units to the left followed by a reflection across the x-axis
b. a rotation of 90 clockwise followed by a translation of 6 units to the left
c. a translation of 5 units to the left followed by a dilation of a factor of 2
d. a reflection across the y-axis followed by a rotation of 180counterclockwise