Which of the following parameters enables NMAP's operating system detection feature?

-sV enables service and version detection on open ports, not operating system identification.

-oS is an output format option that renders results in stylized 'script kiddie' text, not a scanning or detection feature.

-sR was a legacy RPC scan flag that has since been deprecated and was never used for OS detection.

The -O flag instructs Nmap to enable OS detection, which works by sending a series of specially crafted TCP and UDP probes and comparing the responses against a database of known operating system fingerprints. This is the standard and correct flag for identifying the operating system of a remote host in Nmap.