What is a key feature of complete metamorphosis in insects?

Complete metamorphosis in insects is characterized by a distinct transition through different life stages: egg, larva, pupa, and adult. The key feature denoted in the correct choice highlights that during this process, insects go through distinct larval and pupal forms, which are markedly different from each other and the adult stage.

The larval form typically has a different morphology and lifestyle, often focusing on feeding and growth, while the pupal stage represents a transformative phase where the insect undergoes substantial internal and external changes before emerging as an adult. This drastic change is a hallmark of complete metamorphosis, as each stage serves a unique purpose in the life cycle of the insect, allowing for specialization and adaptation to different environments and stages of life.

In contrast, other choices suggest characteristics that do not apply to complete metamorphosis. Some insects may not have two life stages, significant physical changes happen during development, and the forms at various life stages are not consistent; thus, they do not accurately describe complete metamorphosis.