Which of the following describes an example of symmetry?

A butterfly's wings provide a clear example of symmetry due to their identical shape, size, and position on either side of the butterfly's body. This bilateral symmetry allows for a mirror-image relationship between the left and right wings, which helps in illustrating the concept of symmetry effectively.

In contrast, a circle embodies radial symmetry but not bilateral symmetry, as it is symmetrical around its center at any angle. While a square typically demonstrates symmetry, the option stating "a square with unequal sides" would not exhibit true symmetry due to the lack of equal lengths in all sides. A 3D sculpture may or may not exhibit symmetry, as it can vary greatly in design and structure. Therefore, the characteristics of the butterfly’s wings most precisely and explicitly reflect the fundamental definition of symmetry, making it the best answer in this context.