Which sentence demonstrates proper nonrestrictive clause punctuation?

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

Answer: (A)

The main idea here is how nonrestrictive clauses are punctuated. A nonrestrictive clause adds extra information about the noun but isn’t essential to identify which noun we’re talking about, so it should be set off by commas on both sides. In this sentence, the clause “which has the map” is extra information about the book, and the core meaning remains “The book is mine” if you remove that extra detail. Placing commas around the nonrestrictive clause signals that it’s optional information, so the sentence reads smoothly and correctly as: The book, which has the map, is mine.

The other options mishandle this punctuation or the type of clause. Using “which” without commas can make the clause read as essential information, which isn’t appropriate for a nonrestrictive use. Using “that” would typically introduce a restrictive clause with no commas, changing how the information is mapped to the noun. And inserting a comma after the clause, as in the last option, disrupts the flow and isn’t correct for this nonrestrictive construction.