You are presented with the quiz "What organisms are a source of food for many species of fish?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "sponges are a source of food for many species of fish" and "like sponges, they are attached to the ocean floor". So, what's the best answer to the question?
Possible answers:
(1). remains of prehistoric life;
(2). whales;
(3). organic matter;
(4). sharks;
(5). gastropod shells;
(6). those on the ocean floor;
(7). Something made from fermented ricce;
(8). humans;
(6).