Question: What happens to the current AS keys KRRCenc, KUPenc (if available), and KUPint (if available) after the ng-eNB sends the RRC Release message to the UE?
Option 1: The ng-eNB keeps all the current AS keys.
Option 2: The ng-eNB deletes KRRCenc, KUPenc (if available), and KUPint (if available) but keeps KRRCint.
Option 3: The ng-eNB saves the pair of {NCC, NH} in the current UE AS security context and deletes all the current AS keys.
Option 4: The ng-eNB stores the sent I-RNTI together with the current UE context including the remainder of the AS security context.
Explanation: According to the text, after sending the RRC Release message to the UE, the ng-eNB deletes the current AS keys KRRCenc, KUPenc (if available), and KUPint (if available) but keeps the current AS key KRRCint.