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

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)

Nonrestrictive clauses provide extra information about a noun and are set off by commas. In this sentence, “who wrote the book” adds details about the author but isn’t needed to identify which author is being talked about; you could remove it and still say, “The author won an award.” Because the information is nonessential, it must be enclosed by commas on both sides: The author, who wrote the book, won an award.

The other versions don’t use this punctuation pattern correctly. If the clause isn’t surrounded by both commas, the information isn’t clearly nonessential, and the sentence loses its proper nonrestrictive meaning or becomes hard to parse.