相關(guān)單詞同義詞selectable, hit, or, miss, elective subjects, 近義詞 voluntary 自愿的, elective 選舉的, discretionary 自由裁量的, possible 可能的, free 自由的反義詞obligatory, 強(qiáng)制性的compulsory, 強(qiáng)制的臨近詞opulence, option, optionally, optionality, optional fee, optional rate, optional halt, optional part, optional list, optional bond, optional tour, optional meet相似詞optimization, optimize, optimum, option, optometrist, opulent, opus, or, 返回 optional