Final answer:
Most animals, from cnidarians to mammals, share the characteristic of sexual reproduction, which involves offspring passing through developmental stages to establish a determined body plan.
Step-by-step explanation:
The characteristic shared among animals ranging from cnidarians to mammals is c) sexual reproduction. While there is considerable diversity in the animal kingdom, most animals reproduce sexually. This means that offspring pass through a series of developmental stages to establish a determined body plan. This feature is consistently observed from simple organisms like cnidarians, which have radial symmetry and are diploblastic (having two germ layers), to complex organisms such as mammals, which have bilateral symmetry and are triploblastic (having three germ layers).