已知序列x[k]={1,1,2,3; k=0,1,2,3}和y[k]={1,2,3,4; k=0,1,2,3}的自相关函数Rx[n]为（ ）。

A、{3,8,14,21,13,7,4; k=-3,-2,-1,0,1,2,3}
B、{3,5,9,15,9,5,3; k=-3,-2,-1,0,1,2,3}
C、{4,7,13,21,14,8,3; k=0,1,2,3,4,5,6}
D、{3,8,14,21,13,7,4; k=0,1,2,3,4,5,6}