The correct answer is "Angles".

If two sides of a triangle are congruent, then the angles opposite those sides are congruent. This is a property of isosceles triangles, where two equal sides imply that the base angles are also equal.

Would you like further details or explanations?

Here are some related questions for further understanding:

1. What defines an isosceles triangle?
2. How can you prove that angles opposite congruent sides are also congruent?
3. What are the properties of an equilateral triangle?
4. Can a triangle have more than two congruent sides? What type of triangle would that be?
5. How does the concept of congruence apply to different shapes, like quadrilaterals?

Tip: In any triangle, if two angles are congruent, the sides opposite those angles are also congruent. This property works both ways!