Predict the output

import java.util.$*$;

public class TryStack

$\{$

public static void main$($String$[]$ args$)$

$\{$

Stack s$1=$new Stack$()$;

s$1.$push$("$Abc$")$;

s$1.$push$("$def$")$;

s$1.$push$("$pqr$")$;

s$1.$push$("45")$;

s$1.$add$(2,"$xyz$")$;

System.out.print$($s$1)$;

$\}$

$\}$

a$.$

$[$Abc$,$ def, xyz$,$ pqr$,45]$

b$.$

error

c$.$

$[$Abc$,$ xyz$,$ pqr$,45,$ def$]$

d$.$

$[$Abc$,$ xyz$,$ pqr$,45]$