Question

all right angles are congruent. a. undefined terms b. defined terms c. postulates d. theorems

Explanation:

A theorem is a statement that can be proven. The statement "All right - angles are congruent" can be proven using geometric principles. It is not an undefined term (basic building - blocks like point, line, plane), not a defined term (like a triangle which is defined in terms of other concepts), and not a postulate (an accepted statement without proof).

Answer:

D. Theorems