In this geography-based odd-man-out question, select the odd word from the given alternatives.

Introduction / Context:
This question tests basic geography and classification knowledge. The given words name large natural features of the Earth. Three of them are forms of water bodies, while one is a dry landform with very little water. The objective is to recognise which term does not belong to the water-related category and mark it as the odd-man-out.

Given Data / Assumptions:

• Options: Ocean, Sea, Desert and River.
• We use standard geographic meanings.
• We aim to classify them by whether they are water bodies or not.

Concept / Approach:
Ocean, Sea and River are all different kinds of water bodies: oceans are the largest saltwater bodies, seas are smaller saltwater bodies partly enclosed by land and rivers are flowing freshwater bodies. A desert, on the other hand, is a dry region with very low rainfall and very little surface water. This fundamental difference in the presence of water is the key idea for classification.

Step-by-Step Solution:
Step 1: Consider Ocean. An ocean is a huge, continuous body of saltwater that covers most of the Earth's surface. It is clearly a water body. Step 2: Consider Sea. A sea is a large body of saltwater, typically connected to an ocean and partly enclosed by land. It is also a water body. Step 3: Consider River. A river is a natural freshwater stream that flows across land, eventually joining a sea, lake or ocean. It is again a water body. Step 4: Consider Desert. A desert is a large region of very low rainfall, often sandy or rocky, where vegetation and surface water are scarce. It is a type of dry landform, not a water body. Step 5: Summarise. Ocean, Sea and River all represent water bodies, while Desert represents a dry land area. Step 6: Conclude that Desert is the odd word among the four.

Verification / Alternative check:
Even if we categorise features by climate or moisture level, the result is the same. Oceans, seas and rivers are associated with abundant water, humidity, and often support a wide range of aquatic life. Deserts are associated with aridity, scarce water, and specialised flora and fauna adapted to dryness. From both the perspective of physical geography and climate, Desert stands apart from the other three terms, confirming our choice.

Why Other Options Are Wrong:
Ocean is not odd because it clearly belongs to the group of water bodies along with Sea and River. Sea also fits this category as a saltwater body. River is a flowing water body and is grouped naturally with the others. Since these three options are all examples of water bodies, they cannot be considered the odd-man-out. Only Desert does not contain surface water as a defining feature and therefore is the correct answer.

Common Pitfalls:
Some learners may overcomplicate the question by thinking about whether the feature is salty or fresh, or whether it is still or flowing. However, those secondary distinctions split the water bodies among themselves and do not single out a unique odd option. The main and simplest category distinction is water body versus dry landform. Keeping your focus on the broadest category prevents such confusion in reasoning questions.

Final Answer:
The odd word is Desert, because Ocean, Sea and River are all water bodies, whereas Desert is a dry landform with very little water.