A 3 month old infant girl is brought to the physician because of an upper respiratory tract infection. She has had intermittent tonic muscle contractions and two previous upper respiratory tract infections since birth. She has low set, notched ears. Her serum calcium concentration is 4 mg/dl. Abnormal development of which of the following structures is most likely cause of her disorder? a. First and second branchial grooves b. First and second pharyngeal pouches c. Second branchial groove and second pharyngeal pouch d. Third and fourth branchial groove e. Third and fourth pharyngeal pouches.