Which of the following best describes a nanometer?

• A. A unit of time equal to 10^{-9} seconds
• B. A unit of volume equal to 10^{-9} liters
• C. A unit of length equal to 10^{-9} meters
• D. A unit of mass equal to 10^{-9} grams

Answer: (C)

Verified step by step guidance

1. Understand that the prefix 'nano-' in the metric system denotes a factor of \$10^{-9}$, which means one-billionth of the base unit.
2. Recall the base units for common physical quantities: length is measured in meters (m), time in seconds (s), volume in liters (L), and mass in grams (g).
3. Recognize that a nanometer (nm) is a unit of length, so it must be related to meters.
4. Express the nanometer in terms of meters using the prefix nano: \$1\ \text{nm} = 10^{-9}\ \text{m}$.
5. Conclude that a nanometer is a unit of length equal to \$10^{-9}$ meters, distinguishing it from units of time, volume, or mass.