Question: During an inter-RAT handover to E-UTRAN, what primarily determines whether the `Tsearch` component of the interruption time (`Tinterrupt`) is set to 0 ms or a non-zero value (up to 80 ms)?
Option 1: The type of PRACH configuration used in the target cell.
Option 2: Whether the UE has previously identified the target cell within the last 5 seconds.
Option 3: The signal quality of the target cell at the time of handover command reception.
Option 4: The specific TDD option (e.g., 3.84 Mcps, 1.28 Mcps, or 7.68 Mcps) employed by the target cell.
Explanation: `Tsearch` is set to 0 ms if the target cell is already known to the UE (identified within the last 5 seconds). Otherwise, for an unknown cell with sufficient signal quality, `Tsearch` can be up to 80 ms, highlighting the importance of prior cell identification in minimizing handover interruption time.