instruction:
Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.
question:
Fact: Starfish lack respiratory and excretory systems. 
Question: What kind of animal doesn't have a respiratory or excretory system?
answer:
starfish.


question:
Fact: Ejaculation of sperm can be inhibited by bacterial infection. 
Question: Bacterial infection can inhibit ejaculation of what?
answer:
sperm.


question:
Fact: hearing is used for sensing  vibrations by animals. 
Question: Hearing is used for sensing _ by animals?
answer:

vibrations.