What describes complete metamorphosis in insects?

The description of complete metamorphosis in insects is accurately captured by the inclusion of a pupa stage in their life cycle. Complete metamorphosis, also known as holometabolism, involves four distinct life stages: egg, larva, pupa, and adult. The pupa stage is crucial because it is during this phase that the larva undergoes significant transformation, reorganizing into the adult form. This process facilitates a complete reorganization of the insect's body structure, leading to a marked difference between larval and adult forms.

Insects that undergo complete metamorphosis exhibit a dramatic change in appearance and function between the larval and adult stages. Because the pupa stage is a characteristic feature of this developmental process, its inclusion in the definition is vital to understanding the differences between it and incomplete metamorphosis, where no distinct pupa stage is present. The other options do not accurately reflect the characteristics of complete metamorphosis. For example, the adult does not resemble the larva in structure or ecology, and the process involves multiple developmental stages, not just one. Additionally, larvae typically look quite different from the adults they will become.