【正确答案】Universal grammar，als known as principles-and- parameters theory，is a system of linguistic knowledge and a human species-specific gift which exists in the mind or brain of a normal human being．It consists of a set of general conditions，or general principles，that generate phrases and at the same time restrain the power of Move α，thus preventing this rule from applying in certain cases．UG also contains a set of parameters that allow general principles to operate in certain ways，according to which particular grammars of natural languages vary．