The PassGuide network consists of a series of routers that are all configured for IBGP. Which one of the following IBGP characteristics is true（）

A、The IBGP routers must always be fully meshed.

B、The IBGP routers can be in a different AS.

C、The IBGP routers must be directly connected.

D、TThe IBGP routers do not need to be directly connected.

E、None of the other alternatives apply are true