相关单词同義詞selectable, hit, or, miss, elective subjects, 近義詞 voluntary 自願的, elective 選擧的, discretionary 自由裁量的, possible 可能的, free 自由的反義詞obligatory, 強制性的compulsory, 強制的臨近詞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