案例:　张某夫妇于2003年2月底来北京打工,在海淀区合租了一间平房居住,租期为一年。并预交了房东半年租金。4月底,北京流行“非典”。两人因害怕染上“非典”,准备回家,于是向房东要求退还此后四个月的租金,房东认为是张某夫妇违约,不肯退还。张某夫妇却坚持认为这是不可抗力 Case: Zhang and his wife came to Beijing to work at the end of February 2003 and lived together in a bungalow in Haidian District for a term of one year. And pre-paid the landlord six months rent. By the end of April, Beijing was endemic to “SARS.” The two were afraid of contracting “SARS” and were ready to go home, so they asked the landlord for the rent for the next four months. The landlord believed that Zhang and his wife were in default and refused to return. Zhang couple insisted that this is force majeure