Improve the following sentence, if necessary, by choosing the most appropriate option: "This book is the more interesting of the three."

Introduction / Context:
This question checks your understanding of comparative and superlative forms of adjectives. When we compare three or more items, English normally uses the superlative degree, not the comparative. The original sentence uses "more interesting" even though it clearly talks about three books. You must select the correct degree of comparison and the correct article usage.

Given Data / Assumptions:
- Original sentence: "This book is the more interesting of the three."
- There are exactly three books being compared.
- The speaker wants to say that one specific book stands out as the best or most interesting among them.
- We need to choose the option that expresses this idea correctly and naturally.

Concept / Approach:
In English grammar, the comparative form (for example "more interesting") is used to compare two items. The superlative form (for example "most interesting") is used when comparing more than two items and identifying the highest or lowest degree among them. With the phrase "of the three", the appropriate choice is the superlative "the most interesting". The definite article "the" is required before a superlative when it refers to a specific item in a group.

Step-by-Step Solution:
Step 1: Identify that the sentence refers to "the three" books, so more than two items. Step 2: Recall the rule: two items require comparative, three or more items require superlative. Step 3: Replace "more interesting" with "most interesting". Step 4: Keep the article "the" because we are pointing to one specific book in a definite group: "the most interesting of the three." Step 5: The improved sentence is "This book is the most interesting of the three."

Verification / Alternative check:
Option A "the interesting of the three" is wrong because it lacks any comparative or superlative form and sounds incomplete. Option C "most interesting of the three" omits the article "the", which is normally required in this structure, although it might appear occasionally in informal speech. "No improvement" is invalid because the use of "more interesting" with "of the three" breaks the common degree of comparison rule. Therefore, option B is both grammatically correct and stylistically standard.

Why Other Options Are Wrong:
- "the interesting of the three": does not show comparison and is unidiomatic.
- "most interesting of the three": missing "the" makes the sentence sound incomplete in formal English.
- "No improvement": fails to correct the misuse of the comparative degree.

Common Pitfalls:
A typical error is to add "more" or "most" without checking how many items are being compared. Remember the pattern: for one syllable adjectives, use "-er" and "-est" (tall, taller, tallest). For longer adjectives, use "more" and "most" (interesting, more interesting, most interesting). Always pair the superlative with "the" when it refers to a specific member of a group, such as "the tallest of the three" or "the most intelligent in the class".

Final Answer:
The correct improved sentence is This book is the most interesting of the three.