The stage of gradual metamorphosis that resembles the adult insect is the nymph. In this life cycle, nymphs are immature forms of insects that undergo several molts before reaching adulthood. Unlike other stages, such as larvae or caterpillars, nymphs maintain a similar shape and overall body plan to the adult form but are typically smaller and not fully developed. This allows them to feed and grow in an environment similar to adults, providing a cohesive transition into the final stage of their lifecycle.
In contrast, caterpillars are larval forms that will undergo significant transformation during their metamorphosis into butterflies or moths, and they do not resemble the adult stage until they complete their full life cycle. Chrysalis refers to the pupal stage of certain insects, which is a non-feeding stage where transformation occurs, and is quite different from the adult form. The larva stage, similar to the caterpillar, often looks nothing like its adult counterpart and undergoes substantial changes during metamorphosis. Therefore, the nymph stage is distinct in its resemblance to the adult form, making it the correct choice.