Question

The figure below shows triangle NRM with r2 = m2 + n2.



Ben constructed a right triangle EFD with legs m and n, as shown below.



He made the following table to prove that triangle NRM is a right triangle.

Statement Reason
1. r2 = m2 + n2 1. Given
2. f2 = m2 + n2 2. Pythagorean Theorem
3. f2 = r2 3. Substitution
4. f = r 4. ?
5. Triangle NRM is congruent to triangle EFD 5. SSS Postulate
6. Angle NRM is a right angle 6. CPCTC
7. Triangle NRM is a right triangle 7. Angle NRM is a right angle






Which reason best fit