Which two ways to manage scalability issues inside an IBGP domain with 20 or more routers are recommended?

Which two ways to manage scalability issues inside an IBGP domain with 20 or more routers are
recommended? (Choose two.)

A.
Configure route reflectors.

B.
Use OSPF instead of EIGRP as an underlying routing protocol.

C.
Create a full mesh at Layer 1.

D.
Configure confederations.

E.
Configure static routes between all routers.