question: object:vibration:sound waves
choices.label: A B C D
choices.text: land:cultivation:harvest aircraft:delay:staying rock:weather:sand wire:conducting electricity:magnetic field
explanation: "sound waves" are formed by "vibrations" of "objects", and "sound waves" are physical phenomena. "harvest" is not necessarily obtained by "cultivation" of "land" passenger "staying" is caused by "aircraft" "delays", but "staying" is not a physical phenomenon. "rock" "weathering" is not necessarily caused by "sand", but also debris and soil. a "magnetic field" is formed by "conducting electricity" with a "wire", and a "magnetic field" is a physical phenomenon.
relation: object vibration sound waves R5.1
relation: wire conducting electricity magnetic field R5.1