Which sentence uses a nonrestrictive clause with commas to set off the clause?

• A. The author who wrote the book won an award.
• B. The author, who wrote the book, won an award.
• C. The author, who wrote the book won an award.
• D. The author who wrote the book, won an award.

Answer: (B)

A nonrestrictive relative clause adds extra information about a noun and is set off by commas. In the sentence The author, who wrote the book, won an award, the clause who wrote the book provides nonessential detail about the author. Because this information isn’t needed to identify which author is being talked about, it is correctly enclosed by commas, signaling that the main point is that the author won an award. Removing the clause leaves The author won an award, which still makes sense, showing the information inside the clause is optional. The other options either place the clause without proper commas (making it essential to identify the author) or disrupt the sentence structure with incorrect punctuation, so they don’t properly set off a nonrestrictive clause.