In this analogy question about means of transport, select the related word from the given alternatives: BIRD : AEROPLANE :: FISH : ?

Introduction / Context:
This analogy question relates living creatures with man made vehicles that move in the same medium. You are given the pair BIRD and AEROPLANE and asked to complete the analogy for FISH. Identifying symbolic relationships like creature to vehicle in air and water is a common theme in verbal reasoning questions.

Given Data / Assumptions:
- The first pair is BIRD : AEROPLANE.
- Birds are natural creatures that fly in the air, and aeroplanes are human made machines that also fly in the air.
- The second word FISH is a creature that lives and moves in water.
- The options are FISHERMAN, SOFA, BOAT, and GLASSES.
- We assume a symbolic link where a machine imitates or parallels the motion of a creature in a similar medium.

Concept / Approach:
The essential idea is that an aeroplane is to air what a certain vehicle is to water. Birds move freely in the sky, and aeroplanes are constructed to move through the sky in a comparable way. Similarly, fish move in water, and boats are human made vehicles designed to move through water. Therefore the same type of relationship holds between FISH and BOAT.

Step-by-Step Solution:
Step 1: Recognize that a bird is a living creature that moves in the air.Step 2: Note that an aeroplane is a vehicle built to fly in the air, imitating the ability of birds to travel long distances through the sky.Step 3: Understand that a fish is a living creature that moves in water.Step 4: Identify which option is a vehicle that moves in water. A boat is a watercraft used to travel and transport people or goods across water.Step 5: The other options, fisherman, sofa, and glasses, do not represent water vehicles.Step 6: Therefore BOAT is the item that stands to FISH as AEROPLANE stands to BIRD.

Verification / Alternative check:
Express the analogy in simple descriptive sentences. A bird flies in the air; an aeroplane also flies in the air. A fish swims in water; a boat moves or sails in water. These paired sentences show parallel relationships. If you try to use fisherman, sofa, or glasses in a similar sentence, the analogy breaks because those words represent a person, a piece of furniture, and an object worn on the face, not a water vehicle.

Why Other Options Are Wrong:
- FISHERMAN: This describes a person who catches fish, not a vehicle that moves in water, so the type of relationship is different.
- SOFA: This is a piece of furniture used for sitting, and it has no direct connection with movement in water.
- GLASSES: These are worn on the face to improve vision and do not represent transport in any medium.

Common Pitfalls:
Some candidates may be distracted by the direct association between fish and fisherman, but that relationship is not parallel to bird and aeroplane. The first pair compares a natural flier with a machine flier. The second pair must compare a natural swimmer with a machine that travels in the same environment. To solve such questions correctly, always identify the exact nature of the relationship and ignore options that merely share a loose or superficial link.

Final Answer:
As BIRD relates to AEROPLANE through the medium of air, FISH relates to BOAT through the medium of water. Therefore BOAT is the correct answer.