using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace student
{
    class Program
    {
        static void Main(string[] args)
        {
            int [] a=new int[10];
            int[] b =new int[10];
            int[] c = new int[10];
            int s = 0, m;
            string str,str1,str2,str3;
            for (  m = 0; m < 10; m++)
            {
                Console.WriteLine("请输入{0}学号", m+1);
                str=Console.ReadLine();
                a[m] = Convert.ToInt32(str);
                Console.WriteLine("请输入{0}姓名", m+1);
                str1 = Console.ReadLine();
                Console.WriteLine("请输入{0}数学成绩",m+1);
                str2 = Console.ReadLine();
                b[m] = Convert.ToInt32(str2);
                Console.WriteLine("请输入{0}语文成绩", m+1);
                str3 = Console.ReadLine();
                c[m] = Convert.ToInt32(str3);
            }
            for (  m = 0; m < 10; m++)
            {
                s = s + b[m] + c[m];
            }
            Console.WriteLine("学号是{1},姓名是{2}，数学成绩是{3}，语文成绩是{4},语文数学的和是{5}",a[m],str1 ,b[m],c[m],s);
            Console .ReadKey ();
        }
    }
}
菜鸟初学求解答using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace student
{
    class Program
    {
        static void Main(string[] args)
        {
            int [] a=new int[10];
            int[] b =new int[10];
            int[] c = new int[10];
            int s = 0, m;
            string str,str1,str2,str3;
            for (  m = 0; m < 10; m++)
            {
                Console.WriteLine("请输入{0}学号", m+1);
                str=Console.ReadLine();
                a[m] = Convert.ToInt32(str);
                Console.WriteLine("请输入{0}姓名", m+1);
                str1 = Console.ReadLine();
                Console.WriteLine("请输入{0}数学成绩",m+1);
                str2 = Console.ReadLine();
                b[m] = Convert.ToInt32(str2);
                Console.WriteLine("请输入{0}语文成绩", m+1);
                str3 = Console.ReadLine();
                c[m] = Convert.ToInt32(str3);
            }
            for (  m = 0; m < 10; m++)
            {
                s = s + b[m] + c[m];
            }
            Console.WriteLine("学号是{1},姓名是{2}，数学成绩是{3}，语文成绩是{4},语文数学的和是{5}",a[m],str1 ,b[m],c[m],s);
            Console .ReadKey ();
        }
    }
}
为什么说使用了未赋值的局部变量“str1”求大神指导

string str="", str1="", str2="", str3="";


还存在数组越界的毛病  暂时没时间调试  自己慢慢调试吧

string str = string.Empty;

up   

改成这样吧（也符合你的要求，这个程序很是脆弱，没有进行输入验证，应该进行输入验证最好。）：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace student
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] a = new int[10];
            int[] b = new int[10];
            int[] c = new int[10];
            int s = 0, m;
            string str, str1, str2, str3;
            for (m = 0; m < 10; m++)
            {
                Console.WriteLine("请输入{0}学号", m + 1);
                str = Console.ReadLine();
                a[m] = Convert.ToInt32(str);
                Console.WriteLine("请输入{0}姓名", m + 1);
                str1 = Console.ReadLine();
                Console.WriteLine("请输入{0}数学成绩", m + 1);
                str2 = Console.ReadLine();
                b[m] = Convert.ToInt32(str2);
                Console.WriteLine("请输入{0}语文成绩", m + 1);
                str3 = Console.ReadLine();
                c[m] = Convert.ToInt32(str3);
                s = c[m] + b[m];
                Console.WriteLine("学号是{0},姓名是{1}，数学成绩是{2}，语文成绩是{3},语文数学的和是{4}", a[m], str1, b[m], c[m], s);
            }
            Console.ReadKey();
        }
    }
}