A company has a small network,consisting of a single switch and a single router.The switch has been configured with two vlans,and route-on-a-stick is being configured on the router for inter-vlan routing.A trunk is configured to connect the switch to the router.What is the minimum number of router subinterfaces that are required for all the vlans to communicate?（）

• A、one
• B、three
• C、two
• D、zero