1. The likely reasons are as follows:

• No Internet connection
• Incorrect placement of the <uses-library> element in the AndroidManifest.xml file
• Missing INTERNET permission in the AndroidManifest.xml file

2. Geocoding is the act of converting an address into its coordinates (latitude and longitude). Reverse geocoding converts a pair of location coordinates into an address.

3. The two providers are as follows:

• LocationManager.GPS_PROVIDER
• LocationManager.NETWORK_PROVIDER

4. The method is addProximityAlert().