Concept:Triangles are classified by their side lengths, and a triangle with all three sides equal is called an equilateral triangle.
Explanation:A triangle with all sides equal has the same length for each of its three sides.
Such a triangle is known as an equilateral triangle.
The term "equilateral" comes from "equi" meaning equal and "lateral" meaning sides.
An isosceles triangle has only two equal sides.
A scalene triangle has no equal sides.
A right-angle triangle has one
90∘ angle, but its sides may not all be equal.
Therefore, the triangle with all sides equal is the equilateral triangle.
Answer:C. Equilateral triangle