question: eyes:iris
choices.label: A B C D
choices.text: bones:joints arbor:birch clothes:silk watch:strap
explanation: "iris" is a component of "eyes". both "bones" and "joints" are components of the skeletal system. "birch" is a kind of "arbor". one of the raw materials for "clothes" is "silk". "strap" is a component of "watch".
relation: eyes iris R2.3
relation: bones joints R2.4
relation: arbor birch R2.2
relation: clothes silk R3.7
relation: watch strap R2.3