instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Power plants are where electric power originates. They have electric generators that generate electric current through electromagnetic induction. Answer: power plants
answer:
Where does electric power originate?

question:
Passage: An important function of the circulatory system is transporting oxygen to cells. Answer: circulatory system
answer:
Which system transports oxygens to cells?

question:
Passage: Anaerobic exercises involve the muscles working against resistance. In this case the resistance is the weight of a barbell. Answer: resistance
answer:
When performing anaerobic exercise, your muscles work against what?