Final answer:
Insect eggs are most commonly found in body cavities on a body, such as inside the bodies of other organisms.
Step-by-step explanation:
Insect eggs are most commonly found in d) body cavities on a body. This is because many insects, such as parasitoid wasps, lay their eggs inside the bodies of other organisms, like caterpillars. The insect eggs hatch and the young insects feed on the body of the host organism.