Q: You are presented with the quiz "How do starfish communicate?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "echinoderms use pheromones to communicate with each other" and "modern echinoderms include starfish and sea urchins". So, what's the best answer to the question?

Select from the following. (1). huddle together (2). sound (3). interact (4). Vibrates (5). wave in air (6). during the day (7). Decibels (8). Pheromones
The answer is:
(8).