Which switch instructs Nmap to examine the 100 most commonly used ports for speed?

• A. -F
• B. -p-
• C. -sV --allports
• D. -O

Answer: (A)

The main idea here is speed by limiting the scope of the scan. The fast mode switch is designed to scan only a predefined set of about the 100 most commonly used ports. This dramatically reduces the number of ports Nmap checks, so you get results much faster when you don’t need to see every possible port.

Other options would either broaden the scan or apply unrelated techniques. Scanning all ports (1–65535) takes much longer because Nmap is looking at far more targets. OS detection (-O) focuses on identifying the operating system rather than changing which ports are examined.