Which of the following diagrams indicates the best relation between Lion, Dog…

Concept: In a classification Venn diagram, the diagram's shape encodes the logical relationship between the given items -- three separate, non-touching circles show entities that share no member and where none is a type of another (mutually exclusive, unrelated categories); concentric (nested) circles show a strict hierarchy where each category is a subset of the next; and a larger circle enclosing or touching smaller circles shows categories that are types of a bigger category.

Application: Lion, Dog and Snake are three entirely independent animal categories -- none of them is a type of either of the other two, and they share no members. This is exactly the case of three mutually exclusive, unrelated categories, so the correct diagram must show three separate circles that neither touch nor overlap.

• Three concentric (nested) circles show one category fully contained within another, which is in turn contained within a third -- a strict three-level hierarchy. This does not fit Lion, Dog and Snake, since none of them is a sub-category of the others.

• A large circle with two smaller circles touching its boundary from outside (not inside it, not overlapping it) does not correspond to any standard set relationship among three independent categories.

• A large circle containing two smaller circles side by side inside it shows two categories that are both types of one bigger category. That does not fit three unrelated animals either.

• Three separate circles that neither touch nor intersect correctly show three items that share no members and have no subset relationship -- matching Lion, Dog and Snake exactly.

Hence, the diagram showing three separate, non-overlapping circles is the correct representation of the relationship between Lion, Dog and Snake.