Ichthyosaurs were aquatic reptiles. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are .A) homologous. B) examples of convergent evolution C) adaptations to a common environment D) A, B and C are all correct E) Only two of the responses above are correct.

The correct answer to the question is: E) only two of the responses above are correct.

Explanation:

Only option B) and option C) are correct.Both ichthyosaurs and fish have evolve independently of each other.Both share the same habitat, that is, aquatic habitat.Hence, they share the same environment.As they are exposed to the same aquatic environment they develop features that help them to survive in the same habitat. Hence, they develop dorsal fins and tails that help them to swim in water.These features are developed by means of convergent evolution.However, the dorsal fins and tails of ichthyosaurs and fish are not homologous organs.Homologous organs are those which have got similar structure but are required to perform different functions.But the dorsal fins and tails of both ichthyosaurs and fish help them in swimming.