Question: When does the AMF provide the mapping information between the S-NSSAI to be replaced and the alternative S-NSSAI to a roaming UE?
Option 1: Only when the S-NSSAI included in the allowed NSSAI needs to be replaced.
Option 2: Only when the S-NSSAI included in the mapped S-NSSAI(s) for the allowed NSSAI needs to be replaced.
Option 3: When either of the above conditions is met, and the alternative S-NSSAI is available.
Option 4: When either of the above conditions is met, and there is no PDU session associated with the S-NSSAI to be replaced.
Explanation: According to the text, for roaming UE, the AMF provides the mapping information between the S-NSSAI included in the allowed NSSAI and the alternative S-NSSAI when the S-NSSAI included in the allowed NSSAI needs to be replaced (Option 1), or when the S-NSSAI included in the mapped S-NSSAI(s) for the allowed NSSAI needs to be replaced (Option 2). Additionally, it is up to AMF local policy to determine when to provide this mapping information, e.g., when there is no PDU session associated with the S-NSSAI to be replaced. Therefore, Option 4 is the correct answer as it combines both conditions and adds an additional condition that is mentioned in the text.