有以下程序#include main(){ int a,b; for (a=0; a<3; a++) { scanf("%d", &b); switch(b) { case 1: printf("%d,", ++b); case 2: printf("%d,", ++b); default: printf("%d,", ++b); } }}执行时输入:1 2 3<回车> ,则输出结果是
A. 2,3,4,3,4,4,
B. 2,3,4,
C. 2,2,2,3,3,4,
D. 2,3,4,3,4,5,4,5,6