Which stages of insects are present in gradual metamorphosis?

Insects that undergo gradual metamorphosis exhibit three primary life stages: egg, nymph, and adult. This process is characterized by a series of developmental stages where the nymph resembles a smaller version of the adult, rather than going through a distinct pupal stage.

The nymphs gradually mature into adults, typically molting several times as they grow. This leads to a more continuous development without the intermediate pupal stage seen in complete metamorphosis. Both the egg and adult stages serve as crucial points in the life cycle, with the nymph stage being significant for growth and development toward reaching maturity.

In contrast, choices that include the stages of larva and pupa refer to complete metamorphosis, while naiad is associated with aquatic insects, indicating a different developmental pathway. Young is a less specific term and does not clearly define the distinct stages present in typical gradual metamorphosis. Thus, the correct choice reflects the characteristic life cycle stages specific to gradual metamorphosis.