求一至一百的和A，while#include"stdio.h"void main(){ int i=1; sum=0; while(i<=100) { sum=sum+i; //sum=0,需要一个变量保存累加和 i++; } printf("sum=%d\n",sum);}B. do while#include"stdio.h"void main(){ int i=1,sum=0;do{sum=sum+i; i++;}while(i<=100);printf("sum=%d\n",sum);}C. for#include<stdio.h>void main(){ int i,sum; for(i=1,sum=0;i<=100;i++) sum=sum+i; printf("sum=%d",sum);}