Which sequence of transformations shows that triangle a is congruent to triangle b?

a: translate it 10 units to the left, and then rotate it 90 degrees clockwise about the origin

b: reflect it over the x-axis, and then reflect it over the y-axis

c: rotate it 180 degrees about the origin, and then translate it 10 units to the right

d: rotate it 180 degrees about the origin, and then translate it 10 units to the left