C++ :

#include<iostream>
using namespace std;
int a[5];
void f(int idx)
{
	int i;
	if(idx==5)
	{
		bool b1,b2,b3,b4,b5;
		b1=a[1]==1||a[0]==0;
		b2=a[1]!=a[2];
		b3=a[2]==a[3];
		b4=a[3]+a[4]>=1;
		b5=a[0]+a[3]==2||a[4]==0;
		if(b1&&b2&&b3&&b4&&b5)
		{
			for(i=0;i<5;i++)
			{
				if(a[i])
				cout<<char('A'+i);
			}
			cout<<endl;
		}
		return;
	}
	a[idx]=0;
	f(idx+1);
	a[idx]=1;
	f(idx+1);
}
int main()
{
	f(0);
	return 0;
}

Pascal :

program iejfieo;
  var
    a:integer;
  begin
    a:=1;
    write('CD');
  end.

Java :

public class Main {
	public static void main(String[] args) {
		System.out.println("CD");
	}
}