The sequence of transformations are : reflection across the y axis followed by a reflection across the x axis followed by a translation of 2 units up and 1 unit right.
It is true as A consist {7,8,9,10,11,12} and B consists of{9,11,13} and C consist of {7,8,10,12} and D has{7,12} there are the set of numbers from 7 to 13 only so the answer is true that U={7,8,9,10,11,12,13}.
