有如下程序Main( ){int a[3][3] = {{1,2,3},{3,4,5},{5,6,7}}, i,j,s = 0;For(i = 0; i < 3; i++)For(j = 0; j <= 1; 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D