Option B is correct because the -O flag in Nmap is used for operating system detection. However, when trying to maintain a lower profile to avoid detection by an IDS, it's important to adjust the timing of the scan to make it slower and less aggressive. Option A is incorrect because it speeds up the scan, which increases the chances of detection. Option C is incorrect because the --osscan-limit option limits OS detection to promising targets and -T2 makes the scan quite slow but does not specify stealth measures. Option D is incorrect because -O merely activates OS detection without considering stealth or timing concerns.