android - I click HOME button and the program minimizes; but when I press the app icon, the program is launched twice

I have the following
problem:

When I press the Android HOME key, I
can see the "Desktop" and my app icon. Then I press my app icon and my application
launches twice. I don't want open my app
twice.

How my program
works:

I have 4 Activities (A, B, C,
D).

A - The Main Activity: It is the first to
open. It opens the other activity that has a lot of buttons. It's like a Java's main()
method. I show a SplashScreen and I call another Activity. Then I
finish my activity
"A".

B - The Menu Screen: In this
activity, I have some buttons, like a menu. I have a configuration button, update
button, and Login Button. When I click the login button, I finish this activity and open
the Login Screen (Activity "C").

C - The Login
Screen: The user writes the Login and Password. If the login is successful, I finish
this activity and open the Activity "D".

D - The
application main screen: It stays opened all the time and launches another Activities. I
finish this when I want close my
application.

P.S.: I tried change the launchMode
flag (androidManifest.xml), but didn't work.

My
AndroidManifest.xml
bellow:

            android:label="@string/app_name" android:icon="@drawable/icon"
            android:name="MyApplication">
 
            android:label="@string/app_name"

            android:configChanges="orientation">
 

            
             android:name="android.intent.category.LAUNCHER" />

            
 
             android:name="br.com.site.B" android:label="@string/app_name"
            />

             android:label="@string/app_name" />
             android:name="br.com.site.D" android:label="@string/app_name"
            />

And
this is my Activity "A.java"
source:

public class A extends
            Activity {

 @Override

 public void
            onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);

 finish();

            startActivity(new Intent(this, AtualizaDadosFrame.class));

            }
}

I
don't want open my app
twice.

Thanks in
advance!