算法partition中元素交换条件改为i<=p,元素如下:15,14,13,12,15,19,16,18,17,经过一次划分后列表是 ( )

A. 15,14,13,12,15,19,16,18,17  

B. 12,14,13,15,15,19,16,18,17

C. 2,3,4,5,5,6,7,8,9