B

With a target dose of 10 µg/kg/min for an 80-kg patient, the required drug delivery is  
10 µg × 80 kg = 800 µg = 0.8 mg per minute.  
Two 5-mL ampoules give 400 mg, which is diluted to 250 mL → concentration = 400 mg / 250 mL = 1.6 mg/mL.  
Volume needed each minute = 0.8 mg ÷ 1.6 mg/mL = 0.5 mL/min.  
Using a standard adult drip set (~15–16 drops = 1 mL) [Stiles, 1989, PMID 2499192], 0.5 mL corresponds to 0.5 × 16 = 8 drops per minute.