Consider the program given below, in a block-structured pseudo-language with lexical scoping an nesting of procedures permitted.
Program main;
  Var ......
  Procedure A1;
   Var .....
   Call A2;
End A1
Procedure A2;
   Var...
   Procedure A21;
    Var....
    Call A1;
   End A21
   Call A21;
  End A2;
  Call A1;
End main.
Consider the calling chain :
Main → A1 → A2 → A21 → A1
The correct set of activation records along with their access links is given by