The subordinate clause in this sentence is "<span>as do some species of fish, amphibians, mammals, turtles, lizards, snakes, and crocodiles." A subordinate clause is one which is dependent and cannot exist on its own - it has to be located within a larger, independent sentence to make sense. A is incorrect because that is the independent clause, B is incorrect because that is not the complete subordinate clause, and C is incorrect because there is no verb so it cannot be a clause but rather a phrase. </span>
