The correct command is nmap -sU --top-ports 100 -T2 target. This command line uses -sU to initiate a UDP scan. It includes --top-ports 100 to limit the scan to the top 100 most common UDP ports, thus reducing traffic and the likelihood of detection or causing issues on the network. The -T2 option slows down the scan to reduce the chance of overwhelming the devices or triggering any rate limiting or intrusion detection systems. The other options are incorrect as they either scan all ports with -p-, which generates excessive traffic, use -T4 which can be too aggressive for sensitive IoT devices, or -sT which is a TCP scan and would not effectively scan for UDP services.