question: on:off
choices.label: A B C D
choices.text: wheat:rice pain:pleasure profit:non-profit work:rest
explanation: "on" and "off" complement each other. "wheat" and "rice" are both crops. , There are others of the same kind both "pain" and "pleasure" are feelings. There are others of the same kind either "profit" or "non-profit". both "work" and "rest" are part of life, and there are others of the same kinds besides these two.
relation: on off R1.2