Which prefix has the symbol f?

• A. pico- p
• B. nano- n
• C. femto- f
• D. micro- µ

Answer: (C)

This question tests understanding of SI prefixes and their symbols. The symbol f belongs to the prefix femto-, which represents a factor of 10^-15. So 1 femtosecond is 10^-15 seconds, and 1 femtometer is 10^-15 meters. Other tiny prefixes use different symbols: pico- is p (10^-12), nano- is n (10^-9), and micro- is µ (10^-6). The lowercase f is specifically the symbol for femto-, and that distinction matters because SI symbols are case-sensitive and distinct from the other prefixes.