下面程序的输出结果为()。struct st { int x; int*y; } *p; int dt[4]={10,20,30,40}; struct st aa[4]={ 50,&dt[0],60,&dt[1], 70,&dt[2],80&dt[3]}; main() { p=aa; printf("%d ",++p->x); printf("%d ",(p)->x); printf("%d ",++(*p->y)); }A.10 B.50 C.51 D.60 20 60 60 70 20 21 21 31