Question

Does anybody happen to know what the "triangle parts relationship theorem" would be?

I'm doing this question for my Isosceles Triangle quiz, and I was never taught that theorem.

Question:
Since it is given that AB ≅ AC, it must also be true that AB = AC. Assume ∠B and ∠C are not congruent. Then the measure of one angle is greater than the other. If m∠B > m∠C, then AC > AB because of the triangle parts relationship theorem. For the same reason, if m∠B < m∠C, then AC < AB. This is a contradiction to what is given. Therefore, it can be concluded that ________.

Answer 1

Answers:
A.) AB ≠ AC
B.) ∠B ≅ ∠C
C.) ABC is not a triangle
D.) ∠A ≅ ∠B ≅ ∠C

Answer 2

B)