GATE Computer Science (CS) 2012 Solved Paper

Consider the program given below, in a block-structured pseudo-language with lexical scoping and 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