Problem: 
Q: You are presented with the quiz "What is a flower's primary purpose?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "aflower 's purpose is to produce seeds" and "flowers produce seeds for reproduction".   So, what's the best answer to the question?
Answer: To reproduce
Problem: 
Q: You are presented with the quiz "what is the key to life for animals?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "animals require water for survival" and "water is and was the key to life and survival in Palestine".   So, what's the best answer to the question?
Answer: water
Problem: 
Q: You are presented with the quiz "What has a special excretory structure?"   But you don't know the answer, so you turn to your teacher to ask for hints. He says that "some arthropods have special excretory structures" and "all insects are arthropods".   So, what's the best answer to the question?
Answer:
Insects.