Answer:
C. Reflect over the X axis and translate 6 units left
Explanation:
That is the only one that works
A, B, and D are close but don't line up. For one rectangle to line up with another, it had to be in the same place with the same letters at the same corners. For option C, a reflection across the X axis means that rectangle ABCD will flip across the horizontal line. (it matches A'B'C'D now) then a translation 6 units left just moves it six boxes left. It should match A"B"C"D now :)