Geometry

Question Analysis:
This question tests the Triangle Inequality Theorem and equilateral triangle properties.

Key Concept Explanation:
An equilateral triangle must have three equal sides.
The Triangle Inequality Theorem states that the sum of any two sides must be greater than the third side.

Step-by-Step Solution:
Check if all sides are equal: 5 ≠ 10, so it’s not equilateral.
Check the Triangle Inequality Theorem: 5 + 5 = 10 is not greater than 10, so it d...