Question: Which of the following services can utilize in-call modification to change the mode of service within a Public Land Mobile Network (PLMN)?
Option 1: Video Telephony Service
Option 2: Alternate Speech and Group 3 Facsimile Service
Option 3: Short Message Service (SMS)
Option 4: General Packet Radio Service (GPRS) Data Transmission
Explanation: Alternate Speech and Group 3 Facsimile Service supports in-call modification for changing the service mode within a PLMN, allowing for real-time communication adjustments without call interruption.