有如下程序Main(){Int a[3][3] = {{1,2},{3,4},{5,6}}, i,j,s = 0;For(i = 1; i < 3; i++)For(j = 0; j <= i; j++)S += a[i][j]];Printf("%d\n",s);}该程序的输出结果是______。
A.18
B.19
C.20
D.21
正确答案是A