单选题：若有定义:int i=0,x=0;int a[3][3]={1,2,3,4,5,6,7,8,9};则以下程序段运行后x的值为（

若有定义:int i=0,x=0;int a[3][3]={1,2,3,4,5,6,7,8,9};则以下程序段运行后x的值为
for (;i<3;i++) x+=a[i][2-i];






A.0
B.12
C.15
D.18


answer：C