Answer: D.

Explanation:
Let the 'h' be the length of the hypotenuse of the right angle, 'a' be the side corresponding to the square 2 and 'b' be the side corresponding to the square 1 .
Since, area of square =

Then, Area of square 1 =
......................(1)
Area of square 2 =
......................(2)
Area of square 3 =
......................(3)
Using Pythagoras theorem in given right triangle, we get
[from (1),(2) and (3)]