choices.label: A B C D
choices.text: smog:storm freedom:thought bright moon:human brain vacuum:flexible
explanation: without "air", "human beings" cannot survive both "smog" and "storm" refer to weather and are two different weather phenomena. with "freedom", "thought" can be produced "bright moon" and "human brain" have different meanings, and there is no obvious logical relationship. "vacuum" and "flexible" have no obvious logic.
relation: air R5.4
relation: smog storm R2.4
relation: freedom thought R5.4