我刚自学c++,请帮我解决个问题

#include<iostream>
using namespace std;
int a[5][4];
void create()//创建数组
{
for(int i=0;i<5;i++)
{
cout<<"input the "<<i+1<<" student's score:"<<endl;
for(int j=0;j<4;j++)
{
cin>>a[i][j];
}
}
}
int sum_score(int n)//查询第n个学生的总分
{
int sum=0;
for(int i=0;i<4;i++)
sum+=a[n-1][i];
return sum;
}
float aver_score(int m)//查询第m科的平均分
{
float aver=0;
for(int i=0;i<5;i++)
aver+=a[i][m-1];
return aver/5;
}

void main()
{
cout<<"1:create the array:"<<endl
<<"2:search the someone's sumary score:"<<endl
<<"3:search subject's score's average:"<<endl
<<"4:exit."<<endl;
int choice,num;
cin>>choice;
do{
swi