optionallyadv.可选择地optionaladj.任选的optional requirement任选要求optional unemployment选择性失业optional conciliation[经] 非强制性的调解optional calling plan任选呼叫方案optional constituents状元optional service call任选业务呼叫optional legal tender可选择法偿optional sigma-field可选子*-域optional calling plans任选的呼叫方案Optional Parts Request选用零件的申请