Estou criando aplicativos para telefones, mas não posso usá-los em tablets. Não sei por que não posso. Eu uso isso no meu arquivo de manifesto do Android:

android:xlargeScreens="true"

Eu recebo este erro:

erro: Nenhum identificador de recurso encontrado para o atributo 'xlargeScreens' no pacote 'android'

Este é o meu arquivo de manifesto:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="cro.perger.bonbon"
      android:versionCode="5"
      android:versionName="1.4">
    <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="11" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".bonbon"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

            <!-- Broadcast Receiver that will process AppWidget updates -->
        <receiver android:name=".HelloWidget" android:label="@string/w_name">
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
                </intent-filter>
        <meta-data android:name="android.appwidget.provider"
            android:resource="@xml/hello_widget_provider" />
        </receiver>

        <receiver android:name=".SMSReceiver">
            <intent-filter>
                <action android:name="android.provider.Telephony.SMS_RECEIVED" />
            </intent-filter>
        </receiver>    

        </application>
        <supports-screens android:resizeable="true"
                      android:smallScreens="true"
                      android:normalScreens="true"
                      android:largeScreens="true"
                      android:xlargeScreens="true"
                      android:anyDensity="true"/>
    <uses-permission android:name="android.permission.SEND_SMS"></uses-permission>
    <uses-permission android:name="android.permission.RECEIVE_SMS"></uses-permission>
    <uses-permission android:name="android.permission.CALL_PHONE"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission> 
    <uses-permission android:name="android.permission.READ_SMS"/>
</manifest>

O que devo fazer