单项选择题

A.The application server,firewall,and database server on the same VLAN
B.The application server and firewall on one VLAN,and the database server on a second VLAN
C.The application server on one VLAN,and the database server and firewall on a second VLAN
D.The application server and firewall on one VLAN,and the firewall and database server on a second VLAN