________ construction is one whose distribution is functionally equivalent to that of one or more of its constituents, i.e., a word or a groups of words, which serves as a definable Center or Head.
本题考查句法学中的向心和离心结构。 本题阐述的内容为向心结构，向心结构指的是至少有一个直接成份跟整体的语法功能相同的结构叫向心结构。 向心结构里跟整体功能相同的直接成分叫做这个向心结构的核心。