Fishes and worms are diffrent so in other words there systems such as reproduction system are not the same because they will not be able to mate
If it's the first mammal on earth then it's a type of reptile not pretty sure the name and what it looks like but it's a type of reptile for sure even though generation to generation we Been evolve by different types of mammal but before they where all fish a type of fish idk yet though lol.
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Hmm, sorry, I do not think I have learned that yet.
Answer:
a theory should provide the simplest possible (viable) explanation for a phenomenon. and thereby your answer is C