Use the passage to answer the question. For what purpose does the author include the sentence about using the centrifuge as a doorstop? Responses to highlight a problem with a current system to highlight a problem with a current system - no response given to criticize the inventor’s waste of time to criticize the inventor’s waste of time - no response given to indicate a positive opinion of recycling to indicate a positive opinion of recycling - no response given to show a negative opinion of centrifuges