Four objects related to writing and reading are given as options: Book, Pen, Pencil and Wax Colours. Three of them are primarily writing or drawing instruments, while one is different in its main use. From the given alternatives, which word is the odd one out?

Introduction / Context:
This question tests your ability to classify everyday objects based on their primary function. You are given four words that commonly appear in a study environment: Book, Pen, Pencil and Wax Colours. Your task is to identify which one does not belong to the same functional group as the others, making it the odd one out. Such questions are common in aptitude tests for developing logical grouping skills.

Given Data / Assumptions:

• Options: Book, Pen, Pencil, Wax Colours.
• All four items are related to reading, writing or drawing in some way.
• We are looking for one item whose primary role is different from the other three.
• Basic real-life knowledge about stationeries and reading materials is assumed.

Concept / Approach:
The key idea is functional classification. We check how each item is mainly used:

• Pens, pencils and wax colours are tools used to produce writing or drawing marks.
• A book, however, is not a tool for writing; it is an object that already contains written or printed content for reading.

By identifying which item does not function as a writing or colouring instrument, we can select the odd one out.

Step-by-Step Solution:
Step 1: Consider "Pen". A pen is a writing instrument used to put ink marks on paper. It is clearly a tool used for writing. Step 2: Consider "Pencil". A pencil is also a writing or drawing instrument, using graphite or colour lead to create lines and shapes on paper. Step 3: Consider "Wax Colours". Wax colours (crayons) are colouring tools used especially by children for drawing and shading. Step 4: Notice the similarity among Pen, Pencil and Wax Colours: all three are instruments used to create marks on a surface. Step 5: Consider "Book". A book is a collection of pages with printed or written text and images. Its primary role is to be read, not to be used as a writing or colouring tool. Step 6: Therefore, Book is functionally different from the other three items, which makes it the odd one out.

Verification / Alternative check:
One more way to verify your answer is to group the items by their rough category: Group 1: Writing and drawing instruments – Pen, Pencil, Wax Colours. Group 2: Reading material – Book. Because you can place three items in one functional group and only one item in another, the single member group is clearly the odd one out.

Why Other Options Are Wrong:
Pen is not odd because it belongs neatly to the category of writing instruments. Pencil is also a common writing and drawing tool, so it matches Pen and Wax Colours. Wax Colours are drawing tools used for colouring, sharing the same functional category as Pen and Pencil. Only Book does not act as an instrument; instead, it is an object to be read, so it is the different one.

Common Pitfalls:
Sometimes students overthink and consider that a book might indirectly be related to writing because authors use writing instruments to create its content. However, in reasoning questions, we consider the direct and primary use of each object. Another pitfall is focusing on physical appearance (for example, all items might be found on a study table) instead of actual function. Always focus on the central usage pattern.

Final Answer:
The word that differs in primary function and is therefore the odd one out is Book.