Which sentence properly uses restrictive vs nonrestrictive clauses?

• A. The book that has the map is mine.
• B. The book which has the map is mine.
• C. The book that has the map, is mine.
• D. The book which has the map is mine.

Answer: (A)

Restrictive vs nonrestrictive clauses determine whether the extra information is essential to identify the noun. Here, we need to specify which book, so the clause that describes the book must be essential and not set off by a comma. The sentence uses that to introduce a defining detail—the book that has the map—and no comma, which correctly narrows the reference to the specific book. This makes the meaning clear: among the books, the one that has the map is mine.

Using which without a comma doesn’t align with standard usage for a restrictive clause, and if you tried to force a nonrestrictive meaning (as with commas around the clause), you’d be indicating the map is just extra information rather than essential for identifying the book. Adding a comma after the clause would also disrupt the grammar for a restrictive clause and wouldn’t fit the intended meaning.

So, the sentence that uses that with no comma properly marks the essential, identifying information and is the best choice.