Question: What is the expected behavior of a UE when it receives a paging message, considering the implementation option for MUSIM UEs?
Option 1: The UE shall always respond to the paging message.
Option 2: The UE shall ignore the paging message if it's over non-3GPP access.
Option 3: The UE may choose not to respond to the paging message based on information in the message, such as voice service indication.
Option 4: The UE shall initiate a registration procedure for mobility and periodic registration update upon receiving the paging message.
Explanation: According to the text, as an implementation option, the MUSIM UE is allowed to not respond to paging based on the information available in the paging message. This indicates that the UE may choose not to respond under certain conditions, making option 3 the correct answer.