Question: In E-UTRA, what is the primary purpose of the `ue-TxAntennaSelection-SRS-2T4R-2Pairs-r15` field in relation to a User Equipment's (UE) transmission capabilities for Sounding Reference Signals (SRS)?
Option 1: To indicate UE support for selecting one antenna pair out of two available pairs for simultaneous SRS transmission on specific bands.
Option 2: To specify the minimum power requirement for SRS transmission across all bands supported by the UE.
Option 3: To enable or disable SRS transmission based on UE's current bandwidth configuration.
Option 4: To define the maximum number of SRS ports a UE can support in a TDD (Time Division Duplex) mode.
Explanation: This option correctly reflects the purpose of the field, signifying whether a UE can select one out of two antenna pairs for simultaneous transmission of Sounding Reference Signals (SRS) on specific bands, optimizing uplink channel sounding in multi-antenna scenarios.