A detailed _____ helps readers navigate the book.

• A. Indicate
• B. Indigenous
• C. Index
• D. Income

Answer: (C)

An index is a tool that helps readers find topics quickly. A detailed index acts as a topic-focused map, listing terms and subjects with the page numbers where they appear, so you can jump straight to the relevant sections. That makes the sentence natural: a detailed index helps readers navigate the book. While the other words don’t fit as a book feature that guides navigation—indicate is a verb meaning to point out; indigenous describes origin; income refers to money earned—index is the term that specifically describes a navigational aid inside a book. In practice, the index is especially useful for study or research, complementing the table of contents by directing you to exact pages across the whole text.