Which characteristic is common to all insects?

All insects share the characteristic of having three pairs of legs, which amounts to a total of six legs. This trait is fundamental to the classification of insects within the Hexapoda class. The presence of three pairs of legs allows for various forms of locomotion and adaptation in different environments, which is essential for their survival and success as a highly diverse group.

The other options do not apply universally to all insects. The first option about having two pairs of wings applies only to certain insect orders; many insects lack wings entirely. The statement regarding eight legs is characteristic of arachnids, not insects, and thus does not apply. The last option, one pair of antennae, is certainly true for insects but does not distinguish them uniquely, as various other arthropods also possess one pair of antennae. Therefore, the defining feature of three pairs of legs uniquely identifies all insects within their classification.