question: parallel bars:horizontal bars
choices.label: A B C D
choices.text: appendix:heart millimeter:caliber eastern germany:western germany commemoration:anniversary
explanation: "parallel bars" and "horizontal bars" are contradictory to each other. the two together constitute all bar events in men's competitive gymnastics. both the "appendix" and the "heart" belong to human organs, but they are not all the organs of the human body. the units of account of "caliber" include "millimeter". the "eastern germany" and "western germany" are completely complementary, and the two together constitute the entire germany. "anniversary" has the meaning of "commemoration".
relation: appendix heart R2.6
relation: millimeter caliber R3.10
relation: eastern germany western germany R2.5
relation: commemoration anniversary R3.10