把下列词语按顺序重排，并说明理由。  

1．桃花  荷花  迎春花  蜡梅花  桂花    

     顺序：                                                           理由：                              

2．没有  多数  少数  一半  全部    

    顺序：                                                            理由：                                

3．词  字  段  句  篇    

    顺序：                                                            理由：                            

4．元  唐  清  宋  明  

    顺序：                                                            理由：                            

将函数展开为x+4的幂级数，并求此级数的收敛域．