There are three IS-IS routers on a Gigabit Ethernet segment: Router A, Router B, and Router C. Each router is configured in the same area and each routers Gigabit Ethernet interface is configured for Level 1-only. Router A is the Designated Intermediate System (DIS). Each routers IP address on that segment is: Router A: 10.1.1.1/24 Router B: 10.1.1.2/24 Router C: 10.2.2.1/26 Which statement is true about all the adjacencies that exist on that LAN?（）

• A、No routers are adjacent with each other.
• B、Only Router A and Router B are adjacent at Level 1.
• C、Only Router A and Router B are adjacent at Level 2.
• D、All three routers are adjacent with each other at Level 1.