To determine the composition of similarity transformations that maps polygon ABCD to polygon A'B'C'D', we first note two key transformations that are involved:
- Dilation: A dilation with a scale factor less than 1 will reduce the size of the polygon (from ABCD to A'B'C'D').
- Reflection: Since the problem states that polygon ABCD is reflected across the y-axis to create polygon A'B'C'D', we need to account for this as well.
Given this:
- The fact that polygon A'B'C'D' is smaller than polygon ABCD implies that a dilation with a scale factor less than 1 is needed.
- Since the transformation involves reflecting across the y-axis, the composition must include a reflection.
Therefore, the correct answer to the composition of similarity transformations that maps polygon ABCD to polygon A'B'C'D' is:
a dilation with a scale factor less than 1 and then a reflection.