Question: Under what circumstances may a User Equipment (UE) initiate the Media Resource Bundle (MRB) establishment procedure to start receiving a Multimedia Broadcast Multicast Service (MBMS) session in an Evolved Universal Terrestrial Radio Access Network (E-UTRA)?
Option 1: Upon start of the MBMS session, upon (re-)entry of the corresponding Multimedia Broadcast Single Frequency Network (MBSFN) service area, or upon becoming interested in the MBMS service.
Option 2: Upon losing interest in the MBMS service, or when capability limitations start inhibiting reception of the concerned service.
Option 3: When the UE's battery level falls below a certain threshold, or when the UE is in power-saving mode.
Option 4: Upon receiving a dedicated signal from the network to switch to a different frequency band.
Explanation: The correct triggers for initiating the MRB establishment procedure are indeed upon starting an MBMS session, (re-)entering the MBSFN service area, or when the UE becomes interested in receiving the MBMS service. These scenarios indicate a need to establish resources for receiving the multicast/broadcast content, aligning with the purpose of the MRB establishment procedure in E-UTRA networks.