Dear Jenny,
   Please take these things to your brother: his math book, baseball, notebook, CDs, and video tape. The math book is on the dresser. The baseball is under the bed. The notebook is on the bed. The CDs are in the drawer. The video tape is on the table. Thanks!
                                                                                                                                                                            Mom

在中国历史上，国家大一统的观念有悠久历史、深厚的基础，这种国家大统一局面形成始于（   ）