Three words in bold are given, which have something in common among themselves. Out of the four given alternatives, choose the most appropriate description of these three words: knot, watt and fathom.

Introduction / Context:
This verbal reasoning question tests the ability to identify a common conceptual link between seemingly unrelated words. The three given terms are knot, watt and fathom. At first glance, they seem to come from different domains such as sailing, physics or general measurement. The task is to decide which description best captures what all three words have in common, not just what one or two of them might suggest.

Given Data / Assumptions:

• The three words under consideration are knot, watt and fathom.
• Each word is a recognised term in English with one or more meanings.
• We assume standard dictionary meanings, especially those used in science and general knowledge exams.
• We must choose one description that correctly applies to all three words at the same time.
• We are not looking for rare or slang meanings, but the most relevant standard usage.

Concept / Approach:
The best approach is to recall the primary meaning of each word and ask whether that meaning is a unit of some measurable quantity, a job role, an object or some other category. Knot is commonly used as a unit of speed in navigation. Watt is widely known as a unit of power in physics and everyday electricity usage. Fathom is historically used as a unit of length, especially for measuring the depth of water. Seeing them together suggests that they all act as units of measurement for different physical quantities.

Step-by-Step Solution:
Step 1: Recall that a knot is a unit of speed equal to one nautical mile per hour, used particularly in shipping and aviation. Step 2: Recall that a watt is the SI unit of power, defined as one joule per second, and is commonly used to rate electrical appliances and energy usage. Step 3: Recall that a fathom is a unit of length, equal to six feet, traditionally used to measure the depth of water. Step 4: Check whether all three can be described as units. Knot measures speed, watt measures power, and fathom measures length. Step 5: Examine the options and identify the one that states that these are units of measurement. Step 6: Confirm that none of the other alternatives apply equally well to all three words.

Verification / Alternative check:
Knot certainly has a common meaning related to rope, but in technical usage, especially in navigation, the important meaning is as a speed unit. Watt has no meaningful connection with rope or sailing; it is purely a measurement unit. Fathom can be tied to rope when measuring depth with a rope, but the term itself stands for the unit of depth. Since all three are recognised units in measurement systems, the description that they are units of measurement remains consistently correct for each term.

Why Other Options Are Wrong:
The suggestion that they are used by sailors is only clearly true for knot and possibly fathom, but not for watt. The idea that they are used for installing electricity fits watt, but not knot or fathom. The idea that all three are connected with rope might fit knot and sometimes fathom, but watt has no such connection.

Common Pitfalls:
Many students focus on the everyday meaning of knot as tied rope and forget its technical meaning as a speed unit. Others may see the nautical connection and choose the sailors option without checking watt properly. The safest method is to look for a category that fits all three words equally well, rather than one or two of them. Always verify each word against the option before deciding.

Final Answer:
The three words knot, watt and fathom are all units of measurement.