Final answer:
To observe what is happening during an Nmap scan, add the -v option to the command.
Step-by-step explanation:
If the Nmap scan appears to hang and no information is returned, you can add the -v option to the command to observe what is happening. The -v option stands for verbose mode and provides more detailed output. By adding this option, you will be able to see the progress of the scan and any errors or issues that may occur.