void StudentAns(char answer[20])
{
    for (int quest = 1; quest <=20; quest++)
    {
        cout << "Please enter your choice for Question " << quest << endl;
        cin >> choice;
        do
        {
            cout << "You must enter A, B, C, or D.\n";
            cin >> choice;
        }while (choice !='A'|| choice != 'B'|| choice != 'C' || choice != 'D');
        answer[quest-1] = choice;
    }
}

char key[20]=  {'B', 'D','A','A','C','A','B','A','C','D','B','C','D','A','D','C','B', 'B','D','A'};

if (choise == answer[quest])
{
// do things that happends when he have the right answer
} 

while(!(choice =='A'||choice=='B'||choice=='C'||choice=='D'))

//Driver's License Exam


#include <iostream>
#include <stdio.h>
#include <string.h>


using namespace std;

//prototypes
char StudentAns(int );

//global variable
char choice;

int main()
{
	char key[20] = { 'B','D', 'A','A', 'C','A', 'B', 'A', 'C', 'D', 'B', 'C',
		'D', 'A', 'D', 'C', 'B', 'B', 'D', 'A'};

	int i; 
	char answer [20]; 

	for(i = 0; i < 20; i++)
	{
		answer[i] = StudentAns(i);		
	}
	
	return 0;

	int pos = 0;    // initialize pos to point to the 0th index.
	if (!strcmp(choice, key[pos]))
			cout << "This  question is answered incorrectly.\n";
	else 
	{ choice =0;  // initialize counter
	while (choice <=20)
	{
		cout << "you have answered " << choice++ << "correctly.\n";
	}
	}

	if (choice++ >= 15)
	{
		cout << "you have passed the Driver's License Exam.\n";
		cout << "Congratuations!\n";
	}
	else
	{
		cout << "You have failed the Driver's License Exam.\n";
		cout << "Please try again next time.\n";
	}

}

char StudentAns(int i)
{
	
	char choice;
		
	cout << "Please enter your choice for Question " << i+1 << endl;
	cin >> choice;
	choice = toupper(choice);
		
	while(!(choice =='A'||choice=='B'||choice=='C'||choice=='D'))
	{
		cout << "You must enter A, B, C, or D.\n";
		cin >> choice;
	}

	return choice;
}

//Driver's License Exam


#include <iostream>
#include <stdio.h>
#include <string.h>


using namespace std;

//prototypes
char StudentAns(int );

//global variable
char choice;

int main()
{
	char key[20] = { 'B','D', 'A','A', 'C','A', 'B', 'A', 'C', 'D', 'B', 'C',
		'D', 'A', 'D', 'C', 'B', 'B', 'D', 'A'};

	int i; 
	char answer [20]; 

	for(i = 0; i < 20; i++)
	{
		answer[i] = StudentAns(i);		
	}
	
	//return 0; //This exits main before anything else below it is called.         //You're losing a lot of your code. 


	int pos = 0;    // initialize pos to point to the 0th index.
	if (!strcmp(choice, key[pos])) // You still need to fix this by making choice a pointer.
			cout << "This  question is answered incorrectly."<<endl;
	else 
	{ 
             choice =0;  // initialize counter

	     while (choice <=20)
	      {
		cout << "you have answered " << choice++ << "correctly.\n"; //no idea what you're trying to do here; this will always read 'You have answered 1 correctly', because choice never increments.
	      }
	}

	if (choice++ >= 15)
	{
		cout << "you have passed the Driver's License Exam.\n";
		cout << "Congratuations!\n";
	}
	else
	{
		cout << "You have failed the Driver's License Exam.\n";
		cout << "Please try again next time.\n";
	}

}

char StudentAns(int i)
{
	
	char choice;
		
/*	cout << "Please enter your choice for Question " << i+1 << endl;
	cin >> choice;
	choice = toupper(choice); */ //this can be condensed in your loop.
		
	while(!(choice =='A'||choice=='B'||choice=='C'||choice=='D'))
	{
		cout << "For Question: "<<i+1<<"\n Answer with A, B, C, or D.\n";
		cin >> choice;
                choice = toupper(choice);
	}
 //This should work, saves a bit of code, and makes sure that you don't forget the question you are on.

	return choice;
}

char ask(int i) {
   declare holder for the input
   console output the prompt for them
   do {
      ask them for input, inserted into the holder
   } while the input within the holder isn't satisfactory
   return the input in form of the holder
}

void main() {
   declare array, fill with your answer key
   declare empty array to store answers
   declare an int to hold the number of right answers
   for(int i = 0; i < 20; i++) {
            fill the empty array slot by slot according to i, using your asking method
   }
   for(int j = 0; j < 20; j++) {
            check each answer against its respective slot in the answer key
               if right, add 1 to right answers, otherwise add 0
   }
   check number of right answers
       if more than 15, they pass, else they fail
   return 0;
}