obligatoryadj.强制性的;义务的;必须的
obligatory transformation rule必须转换规则
obligatory liabilities insurance强制责任保险
obligatory anaerobic respiration专性缺氧呼吸
obligatory administration system行政强制执行
obligatory internal close juncture限制性内部关音渡
obligatory terminal close juncture限制性终端关音渡(/#/)