Question: What is the primary purpose of the `phy-TDD-ReConfig-TDD-PCell-r12` field in relation to User Equipment (UE) capabilities in an Evolved Universal Terrestrial Radio Access (E-UTRA) network?
Option 1: To indicate UE support for Frequency Division Duplexing (FDD) mode switching on a Primary Cell (PCell).
Option 2: To signal UE capability for enhanced Interference Mitigation and Traffic Adaptation (eIMTA) on all cell types.
Option 3: To define the maximum number of serving cells a UE can support in a Time Division Duplexing (TDD) configuration.
Option 4: To specify whether a UE supports TDD Uplink/Downlink (UL/DL) reconfiguration for a TDD serving cell via PDCCH with eIMTA-RNTI on a TDD PCell, including HARQ feedback adjustments.
Explanation: The `phy-TDD-ReConfig-TDD-PCell-r12` field addresses the UE's capability to adapt to changes in TDD UL/DL configurations on a serving TDD PCell, involving monitoring PDCCH with eIMTA-RNTI for reconfiguration and adjusting HARQ feedback, crucial for efficient wireless communication in TDD modes.