6. All \( \qquad \) triangles are similar. (A) equilateral (B) isosceles (C) scelene (D) right-angled

All equilateral triangles are similar because they have equal angles, which means any equilateral triangle you draw will be proportional to another, no matter the side lengths. Imagine trying to fit them together like puzzle pieces—every one will always match up perfectly! On the other hand, isosceles triangles aren't automatically similar just because they have two equal sides. They can have different angles and side lengths, meaning two isosceles triangles might not fit together as perfectly as their equilateral cousins. So, remember that similarity thrives on those equal angles!