31. What is the reason behind the poor ossification of the bones of fish native to the Mariana Trench? (A) There is not sufficient sunlight in the trench to allow for ossification. (B) They don’t have to have well ossified bones because there are few predators in the Mariana Trench. (C) The fish in the trench must be able to survive on fewer nutrients. (D) The pressure from the deep depth of the trench makes proper ossification impossible.