question: umbrella rib:umbrella
choices.label: A B C D
choices.text: column:ceiling trunk:tree crank:engine rafter:roof
explanation: "umbrella rib" is a part of "umbrella", "umbrella rib" can support the main body. there is no obvious logical relationship between "column" and "ceiling". the "trunk" is the part of the "tree" that supports the main body. the "crank" is part of the "engine" and the "crank" cannot support the main body. the "rafter" is a component that directly bears the weight of the deck and the roof above it. the process of building the "roof" includes building the “rafters".
relation: umbrella rib umbrella R2.3
relation: trunk tree R2.3