读人口密度和城市内商业中心的服务范围示意图，回答图中体现出的人口密度与商业中心之间的关系是（    ）

A.       B.         

C.         D.      E.  

____ ^{A gi}rl named Alice falls down a rabbit hole after an unusual big white rabbit. She finds herself in a land of talking  animals and other fantastic animals, and starts a trip full of adventures(冒险).

____ After a ship accident Crusoe lands on an island. To live he must build a home for himself. He saves a man called Friday. A lot of adventures happen to them on the island.

____ The story is about the Marchi family of four sisters growing up. It shapes the image of the four different characters to the family daily life.

____ ^This is an adventure about a boy called Jim Hawkins. He goes out to sea with a treasure map and finds an island full of treasures. It's a problem­ solving journey to rescue(营救) treasures from dangerous situations.

____ This story is about an emperor who loves clothes very much. Two brothers cheat the emperor to get silver and gold. They tell him that people can't see the clothes unless they are clever. In the parade, everyone says his new clothes are wonderful except a little boy.

已知数列$\left\{a_n\right\}$的前n项和为$S_n$，且$a_1=1,S_n=n^2{a}_n(n\in N^{*})$，可归纳猜想出$S_n$的表达式为（  ）