Question: What triggers the reconfiguration of NCIs for mobile IAB cells in case of an NCI collision with other gNB-DUs?
Option 1: Periodic timer expiration
Option 2: Change in cell load or capacity
Option 3: NCI collision detected by F1-terminating IAB-donor-CU
Option 4: OAM system request for reconfiguration
Explanation: The correct answer is Option 3 because the paragraph states that the F1-terminating IAB-donor-CU serving the mobile IAB-DU can reconfigure the NCIs of the cells served by the mobile IAB-DU in case of an NCI collision with cells of other gNB-DUs. This indicates that the detection of NCI collision by the F1-terminating IAB-donor-CU is the trigger for reconfiguration.