Select the correct choice that completes the sentence below. If none of the angles of a triangle is a right angle, the triangle is called

an acute triangle if all angles are less than 90 degrees, or an obtuse triangle if one angle is greater than 90 degrees. Triangles are fascinating because they come in various forms and having the right terms helps in understanding their properties better! Triangles have been studied since ancient times, with the Greeks making significant contributions, particularly Euclid, who outlined essential principles that are still taught today. The concept of classifying triangles by their angles laid the groundwork for many other mathematical theories and applications across geometry and trigonometry!