Which triangle has no equal sides?

A triangle with no equal sides is identified as a scalene triangle. In a scalene triangle, each of the three sides is of different lengths, and consequently, each of the angles is also different. This distinctiveness is what sets a scalene triangle apart from the others mentioned in the choices.

In contrast, an equilateral triangle has all sides equal in length, which means all angles are also equal, specifically each measuring 60 degrees. An isosceles triangle, on the other hand, has at least two equal sides, which creates two angles that are also equal. The acute triangle refers to the type of angles rather than the side lengths, as it can be scalene, isosceles, or equilateral depending on the specific measurements of its sides.

Thus, the characteristic of having no equal sides is what clearly defines the scalene triangle, confirming it as the correct answer to the question.