Choose the sentence that correctly uses a nonrestrictive clause with commas:

Choose the sentence that correctly uses a nonrestrictive clause with commas:

• 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 relative clauses add extra information and are set off by commas. They don’t change which noun is being talked about; they just add a aside that could be removed without altering the main meaning. In the sentence, the phrase “who wrote the book” gives extra detail about the author, but it isn’t needed to identify which author won the award. So it’s correctly enclosed by commas: The author, who wrote the book, won an award.

The other forms either leave out the necessary commas or place the punctuation in the wrong position, which changes the flow. Without commas, the clause would be restrictive and essential to identifying the author. A sentence that incorrectly places a comma after the clause breaks the standard punctuation pattern for a nonrestrictive clause.