Question: What type of roaming agreement may exist between a Home PLMN (HPLMN) and a Visited PLMN (VPLMN) for a UE to register onto a WLAN Access Network (AN)?
Option 1: LBO (Local Breakout) roaming
Option 2: NSWO (Non-Seamless WLAN Offload) roaming
Option 3: S1 mode roaming
Option 4: N26 interface roaming
Explanation: The correct answer is NSWO roaming, as the paragraph specifically mentions that the HPLMN may have a roaming agreement with a VPLMN for NSWO roaming. This type of roaming allows a UE to register onto a WLAN AN that advertises the HPLMN or a VPLMN with which the HPLMN has a roaming agreement for NSWO roaming.