The answer is: Valid generalization.
A valid generalization is based on the observation of several situations and is concordant with facts in every case. In the example sentence, the evidence about the growth of massive corals has been determined after extensive study and research.
The rest of the options are incorrect because a biased statement has an unfair tendency or prejudice, an opinion is a judgement not based on knowledge or facts, and a hasty generalization is done with excessive speed.