help!!!repeated scentences error!!!

the problem is this..........
the sample output should be

Code:

Enter a grade (A-F):A
Enter a grade (A-F):B
Enter a grade (A-F):A
Enter a grade (A-F):D
Enter a grade (A-F):C
Enter a grade (A-F):D
Enter a grade (A-F):D
Enter a grade (A-F):E
Enter a grade (A-F):C
Enter a grade (A-F):F
number of credit:5
number of pass:9
number of fail:1

BUT.....
it shows up like this...

Code:

Enter a grade (A-F):A
Enter a grade (A-F):
Enter a grade (A-F):
A
Enter a grade (A-F):
Enter a grade (A-F):
A
Enter a grade (A-F):
Enter a grade (A-F):
A
Enter a grade (A-F):
Enter a grade (A-F):
A
Enter a grade (A-F):
Enter a grade (A-F):
A
number of credit:5
number of pass:0
number of fail:0

the program is :

Code:

#include <stdio.h>

int main (){
    int credit = 0, pass = 0, fail = 0, i;   //may be wrong
    char grade;
    
    for(i=1;i<=20;i++)                       //may be wrong
    {
        printf("Enter a grade (A-F):\n");    //may be wrong
        scanf("%c", &grade);
        if (grade<'A'||grade>='C') 
        credit++;
        else
        if(grade<='A'||grade>='E')
        pass++;
        else
        fail++;
    }
    printf("number of credit:%d\n", credit);
    printf("number of pass:%d\n", pass);
    printf("number of fail:%d\n", fail);

    
    system("pause");
    return 0;
}

what's wrong with it?
why are there repeated scentences?

Look at the code modified

Code:

#include <stdio.h>

int main (){
  int credit = 0, pass = 0, fail = 0, i;   //may be wrong
  char grade;

  for(i=1;i<=20;i++)                       //may be wrong
    {
      printf("Enter a grade (A-F):\n");    //may be wrong
      scanf("%c", &grade);
      getchar(); // Added :)
      if (grade<'A'||grade>='C')
        credit++;
      else
        if(grade<='A'||grade>='E')
          pass++;
        else
          fail++;
    }
  printf("number of credit:%d\n", credit);
  printf("number of pass:%d\n", pass);
  printf("number of fail:%d\n", fail);


  system("pause");
  return 0;
}