Which physical characteristic is true of insects?

Insects are defined by having a specific physical structure that includes six legs and three main body parts: the head, thorax, and abdomen. This distinct morphology is a hallmark of the class Insecta, which differentiates them from other arthropods and organisms. Each of the three body parts serves unique functions; for instance, the head houses sensory organs and mouthparts, the thorax is responsible for locomotion as it bears the legs and, in many cases, wings, and the abdomen contains the digestive and reproductive organs.

All other listed choices describe characteristics that do not align with the biological classification of insects. For example, creatures with eight legs, such as spiders, belong to the class Arachnida and possess a different body structure. Additionally, options featuring fewer or different numbers of legs and body parts do not accurately represent the anatomy of insects.