【正确答案】A lingua franca is a variety of language that serves as a medium of communication among groups of people for diverse linguistic backgrounds．A lingua franca must be an agree-upon“common tongue” used by people thrown in social contact for various purposes．For example，the spoken language of modern China PuTongHua，known as the“common speech”，serves as an effective lingua franca among speakers of 56 different nationalities．English is an international lingua franca，used in numerous social and political situations where a common language is asked for．