The interior angles of a triangle add up to 180 degrees. The only set of angles that add up to 180 is 90, 45, 45. 90+45+45=180. So the answer is the last one.
D and E. An acute angle is any angle that is less than 90(a right angle). A is an obtuse angle(more than 90). And B + C are right angles. Hope this helps you!
