Acme Nutrition manufactures a wide variety of vitamin supplements. It has a single manufacturing facility with 3 regional warehouses and 16 district sales offices. Currently the manufacturing facility requires 210 IP addresses; each warehouse requires 51 IP addresses; each district sales office requires 11 IP addresses; and the IP WAN requires 38 IP addresses. if Acme Nutrition plans for 20 percent growth in facilities, how many Class C subnets will the district sales offices require?（）
- A 19 (3 from the warehouse range and 16 from a separate Class C address)
- B 19 (3 from the warehouse block, 15 from a separate Class C block and 1 from the IP WAN block)
- C 20 (4 from the warehouse range,15 from a separate Class C block and 1 from the IP WAN block)
- D 16 (3 from the warehouse range and 13 from a separate Class C address)