Reflecting ABC across the y-axis will negate the x-coordinates, which will place it directly above triangle DEF. Counting down from A to D, B to E and C to F, we see that each is 5 units above the image; this means a translation 5 units down will finish mapping the pre-image to the image. Since they are mapped on top of each other, they are congruent.
So the selected answer would be 2√20 because that comes out to about 8.94 And 4√5 comes out to 8.94 as well but I could be wrong but yeah that's what I think
