What is the primary security purpose of setting android:allowBackup="false" in an Android app's manifest, and what residual risk remains even after setting this flag?

• A.A) It prevents Google Drive Auto Backup and ADB backup; there is no residual risk because all backup vectors are covered
• B.B) It prevents ADB backup (on older Android versions) and Auto Backup; however, a rooted device or physical extraction can still access internal storage directly
• C.C) It prevents the app from appearing in Google Play, reducing the attack surface
• D.D) It encrypts the app's SharedPreferences files using the Keystore automatically