question: forest:vegetation
choices.label: A B C D
choices.text: desert:land reservoir:river white cloud:blue sky black hole:ozone
explanation: "forest" belongs to "vegetation". "desert" is a type of "land". a "reservoir" can be built at the narrow mouth of a "river", but a "reservoir" is not a type of "river". both "blue sky" and "white clouds" appear on sunny days, and "white clouds" are not a type of "blue sky". "black hole" is a kind of celestial body, "ozone" is a kind of gas, and there is no obvious logical relationship between "black hole" and "ozone".
relation: forest vegetation R2.2
relation: desert land R2.2
relation: reservoir river R3.10
relation: white cloud blue sky R2.4