You are answering a USMLE-style medical question. Question: An 8-week-old male presents with his mother to the pediatrician for a well visit. The patient has been breastfed since birth, and usually feeds for 30 minutes every 2-3 hours. The patient’s mother is concerned that her milk production is not keeping up with the patient’s nutritional requirements. She reports that about two weeks ago the patient began regurgitating breastmilk through his nose and mouth after some feeds. She reports that he seems mildly upset during the episodes of regurgitation but usually settles down quickly and is hungry again soon afterwards. The patient’s mother has already tried limiting the volume of each feed, which seems to have reduced the frequency of the regurgitation. She denies any diarrhea, hematochezia, or family history of food allergies. Her older son had a similar problem with vomiting that resolved around 12 months of age. Four weeks ago, the patient’s height and weight were in the 40th and 34th percentiles, respectively. His height and weight are now respectively in the 37th and 36th percentiles. On physical exam, the patient is cooing in his mother’s lap and smiles reciprocally with her. He lifts his head and shoulders off the examination table when placed in the supine position. His abdomen is soft, non-tender and non-distended. Bowel sounds are normoactive. Which of the following is the best next step in management? Options: A) Initiate proton pump inhibitor B) Obtain abdominal ultrasound C) Reassurance and counseling on positioning D) Recommend modification of mother’s diet Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.