question: screw:nut
choices.label: A B C D
choices.text: door panel:door frame roof:floor hour hand:gear cement:mortar
explanation: "screw" and "nut" are used together. "door panel" and "door frame" are used together. the components of the house include the "roof" and "floor", which cannot be used together. the components of the clock include the "hour hand" and "gear", which cannot be used together. "cement" and "mortar" do not need to be used together and can be used alone.
relation: screw nut R3.10
relation: door panel door frame R3.10
relation: roof floor R2.4
relation: hour hand gear R2.4