Step 1: Understanding the Concept:
The question asks for the common characteristic among knot, watt, and fathom.
Step 2: Detailed Explanation:
Knot is a unit of speed (nautical miles per hour), watt is a unit of power, and fathom is a unit of depth (6 feet). All are units of measurement.
Step 3: Final Answer:
Thus, the correct option is (D) They are units of measurement.