Odd-one-out (verbal reasoning) Which word does NOT belong with the others? Choose the single best answer.

Introduction / Context:
This odd-one-out question tests biological vocabulary and category recognition. Four options are internal body parts, but one differs in its type and function. The task is to identify which term does not belong to the same anatomical category as the others by applying basic human biology knowledge about organs versus blood vessels.

Given Data / Assumptions:

• Options: aorta, heart, liver, stomach, pancreas
• Assume standard human anatomy terminology.
• The goal is to find exactly one option that is categorically different from the rest.

Concept / Approach:
Sort each word into the most specific accurate category. An organ is a structurally distinct unit that performs specific functions in a system (for example, digestive or endocrine). A major artery or blood vessel is part of the circulatory conduit system, not an organ that performs digestion, secretion, or pumping by itself. Compare the five options by these definitions and by the system they belong to (digestive, endocrine, cardiovascular).

Step-by-Step Solution:

Verification / Alternative check:
Check system grouping: liver, stomach, and pancreas are digestive system organs; heart is a pump organ of the cardiovascular system; aorta is a conduit vessel within the cardiovascular system. Only aorta fails the 'organ' test in any system, confirming it as the outlier.

Why Other Options Are Wrong:

• Heart: a true organ; not a conduit vessel.
• Liver: organ with multiple metabolic functions.
• Stomach: organ of digestion.
• Pancreas: organ with endocrine and exocrine functions.

Common Pitfalls:
Learners sometimes group 'heart' with 'aorta' under cardiovascular terms and select heart. However, the question is not about system membership alone; it is about item type. Four are organs; one is a vessel. Focus on the organ-versus-vessel distinction to avoid confusion.

Final Answer:
aorta