Step 1: Sentence Comprehension. The sentence implies a doctor's action to transfer a patient to a specialist. The verb must reflect this act of sending or advising.
Step 2: Option Analysis. - (A) referred: Correct verb. "Referred" signifies the doctor directed the patient to a specialist. - (B) deferred: Means to delay or postpone, which is contextually unsuitable. - (C) recommended: While potentially plausible in some scenarios, it does not strongly convey the act of dispatching someone to another specialist. - (D) no change is required: A verb alteration is necessary to align with the context.
Step 3: Determination. Option (A) referred is the accurate choice, best representing the sentence's intended action.