Answer SL5

scope m: a=1    b=2
scope 1: a=1    b=3
scope 2: a=1    b=4
scope 1: a=1    b=3
scope m: a=1    b=2

#include <stdio.h>
int main( void )
{
  int a = 1;
  int b = 2;
  printf("scope m: a=%d\tb=%d\n", a, b );
  
  {
    int b = 3;
    printf("scope 1: a=%d\tb=%d\n", a, b );

    {
      int b = 4;
      printf("scope 2: a=%d\tb=%d\n", a, b );
    }

    printf("scope 1: a=%d\tb=%d\n", a, b );
  }
  
  printf("scope m: a=%d\tb=%d\n", a, b );
  return 0;
}

Comments: Since there are no new declarations of a, each use of the identifier "a" refers to the same variable.

"b", however, is a different story. Each block starts with a declaration of a variable b. There are three different variables "b", each with its own scope.

Notice how, for instance, the "b" used in the second

 printf("scope m: a=%d\tb=%d\n", a, b );