Problem: 
Q: You are presented with the quiz "For plants, what is the difference between running and standing water?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "running water is better able to dissolve oxygen and nutrients than standing water" and "to make it rich in nutrients so the plants are healthier".   So, what's the best answer to the question?
Answer: healthier
Problem: 
Q: You are presented with the quiz "How do starfish communicate with each other?"   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 "echinoderms are represented by the starfish".   So, what's the best answer to the question?
Answer: pheromones
Problem: 
Q: You are presented with the quiz "what can cause a tumor to form?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "cells that divide uncontrollably may form a tumor, or abnormal mass of cells" and "cancer begins when a cell begins dividing uncontrollably".   So, what's the best answer to the question?
Answer:
cancer