question: clean energy:solar energy
choices.label: A B C D
choices.text: hero:warrior windmill:wind energy renewable energy source:plants therapeutic device:massager
explanation: "solar energy" is a type of "clean energy". "heroes" can be "warriors", and "warriors" can also be "heroes". "wind energy" can make the "windmill" turn. "renewable energy source" includes "plants". the two different instruments are different "therapeutic instruments" and "massagers".
relation: solar energy clean energy R2.2
relation: hero warrior R2.7
relation: windmill wind energy R3.10
relation: plants renewable energy source R2.2
relation: therapeutic device massager R2.4