In this odd-man-out question on word pairs, four pairs are given: Zinc – Metal, Aluminium – Metal, Crocodile – Water and Gold – Metal. Three of these pairs show a relationship between a chemical element and its category as a metal, while one pair shows a completely different animal–habitat relationship. Which word pair is the odd one out?

Introduction / Context:
This problem is a verbal odd-man-out question based on word relationships. The four pairs given are Zinc – Metal, Aluminium – Metal, Crocodile – Water and Gold – Metal. In many reasoning exams, such questions check whether you can identify a common relationship pattern and spot the one pair that does not follow it. Here, three pairs represent a chemical element and its classification as a metal, whereas one pair describes an animal and the place where it usually lives.

Given Data / Assumptions:
Zinc is a chemical element that belongs to the category of metals.
Aluminium is also a chemical element categorized as a metal.
Gold is a well known precious metal and a chemical element.
Crocodile is a reptile and the word Water indicates its common habitat, not its chemical category.
Exactly one pair does not match the element–metal pattern.

Concept / Approach:
The concept used here is relationship classification. Three of the given pairs have the form “element – category” where the category is Metal. Zinc, Aluminium and Gold are all elements of the periodic table, and each is a metal. The fourth pair, Crocodile – Water, shows a different type of relation: “animal – habitat”. While the pair is meaningful, it is not comparable to the element–metal classification used in the other three pairs, and that is why it should be treated as the odd one out.

Step-by-Step Solution:
Step 1: Analyze Zinc – Metal. Zinc is a chemical element, and its category is Metal, so this pair is of type element–category. Step 2: Analyze Aluminium – Metal. Aluminium is again a chemical element categorized as a metal, matching the same type of relation. Step 3: Analyze Gold – Metal. Gold is a precious chemical element and clearly belongs to the metal category, so this pair is also element–category. Step 4: Analyze Crocodile – Water. Crocodile is a reptile and Water describes the habitat where it spends much of its life, making this an animal–habitat pair instead of element–category. Step 5: Conclude that Crocodile – Water is the only pair that does not relate a chemical element to the category Metal, so it is the odd one out.
Verification / Alternative check:
To verify, try replacing “Metal” with a different classification word for each of the element pairs. For example, Zinc – Non-metal would be incorrect, as Zinc is a metal by definition. The same applies to Aluminium and Gold. However, if you attempt to fit Crocodile into the same form, it does not work because Crocodile is not an element, and Water is not a classification category like Metal. Instead, Water is the environment in which the animal lives. This difference in the type of connection confirms that Crocodile – Water is fundamentally different from the other three pairs.

Why Other Options Are Wrong:
Zinc – Metal correctly shows that Zinc is classified as a metal, so it fits the main pattern and is not odd.
Aluminium – Metal also fits the same element–metal classification, so it belongs to the majority group.
Gold – Metal again represents an element and its category and therefore is completely consistent with the key relationship.
Crocodile – Water, however, does not involve an element or a metal classification and stands out as an animal–habitat pair instead.

Common Pitfalls:
A common pitfall is to focus on the idea that both Crocodile and Water are related to nature and therefore might seem to fit with elements, but this mixes different categories of things. Elements and metals belong to chemistry, while crocodiles and water belong to biology and environment. In odd-man-out questions, you should pay attention to the type of relationship, not just the broad topic. Another mistake is to overthink and search for hidden scientific details, when the classification difference is already clear and sufficient.

Final Answer:
The only pair that does not show an element–metal classification and is therefore the odd one out is Crocodile – Water.