The answer is A. 2.8. Explained: I used the distance formula (or the top part of Pythagorean theorem) of d=square root of (x2-x1)+(y2-y1). Using points A (0,2) as (x1,y1) and point B (2,4) as (x2,y2) to put inside the distance formula. d=square root of (2-0)^2+(4-2)^2= square root of (2)^2+(2)^2= square root of (4+4)= square root of 8 which equals 2.8. Since triangle ABC is congruent to triangle EFD then since side AB equals 2.8 then side FE equals 2.8.