Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: Power plants are where electric power originates. They have electric generators that generate electric current through electromagnetic induction. Answer: power plants
[A]: Where does electric power originate?

[Q]: Passage: Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. Only with fluorine does oxygen form compounds in positive oxidation states. Answer: positive oxidation states
[A]: Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. only with fluorine does oxygen form compounds in this?

[Q]: Passage: Like mammals and birds, and unlike other reptiles, crocodiles have a four-chambered heart. But, unlike mammals, blood with and without oxygen can be mixed. Answer: four
[A]:
Like mammals and birds, and unlike other reptiles, crocodiles have how many chambers in their heart?