Geometry

Question Analysis:
This question assesses understanding of the hierarchy of triangle classifications.
The main focus is recognizing that equilateral triangles are a subset of isosceles triangles.

Key Concept Explanation:
Equilateral triangle: All sides and angles equal (each angle = 60°).
Isosceles triangle: At least two sides equal (equilateral satisfies this).

Step-by-Step Solution:
An equilateral triangle has three equal sides.
Since it has at least two equal sides, it is isosceles by definition.

Option Analysis:
A) Incorrect: All angles are 60° (acute).
B) Correct...