Answer: Corresponding parts of congruent triangles are congruent.
Explanation:
When two triangles are congruent then their corresponding parts of are also congruent.
In the given proof, Statement 5 says Δ NRM≅ Δ EFD
which provides that ∠NRM=∠EFD=90 ° because of the property that corresponding parts of congruent triangles are congruent.
Therefore, Corresponding parts of congruent triangles are congruent.
best fits statement 6.