3)РPolygamy, head-hunting, infanticide, gladiatorial fighting and dueling are practiced only in munities or practiced in certain historical times. They are considered immoral, improper and abnormal elsewhere or in modern times.Рfundamental/essential/vitalРFundamental suggests sth. that is a basic thing without which an entire system would collapse. (强调基础或根基是无形事物或抽象事物)РEssential suggests sth. that is the very basic nature of a thing. (必不可少的特点,本质)РVital suggests sth. that is necessary to a thing’s existence, continuation or well-being.(强调对某物存在、发展极为重要)РExample:РMonarchy had undergone fundamental changes.РTo seek truth is one of the fundamental principles of Mao Zedong thought.РSocial stability is essential to economic construction.РTransportation munication are vital to economic development.