Final answer:
The sentence that uses commas correctly is option B: The doctor, who opened his new office last month, had more patients than he could handle.
Step-by-step explanation:
The sentence that uses commas correctly is option B:
- The doctor, who opened his new office last month, had more patients than he could handle.
In this sentence, the commas are used correctly to set off the nonessential phrase who opened his new office last month. This phrase provides additional information about the doctor but is not necessary to understand the main subject and verb of the sentence.
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