Which sentence correctly uses a nonrestrictive clause with commas?

• A. The scientist who discovered the anomaly won an award.
• B. The scientist, who discovered the anomaly, won an award.
• C. The scientist, who discovered the anomaly won an award.
• D. The scientist who discovered the anomaly, won an award.

Answer: (B)

The sentence uses a nonrestrictive relative clause, which gives extra information about the scientist without narrowing down who is being talked about. The phrase who discovered the anomaly is parenthetical and is set off by commas: The scientist, who discovered the anomaly, won an award. Because this information is not essential to identify the scientist, it can be removed and the sentence still makes sense: The scientist won an award.

Other options don’t fit this pattern. Without the commas, the clause who discovered the anomaly would be restricting the scientist, implying there are multiple scientists and only the one who discovered the anomaly won an award. Missing the closing comma around the parenthetical clause or misplacing it also breaks the standard nonrestrictive punctuation, making the sentence awkward or grammatically incorrect.