You are using standalone cisco aironet 1400 series wireless bridges for a nine-mile point-to-point wireless link between two buildings.
Which distance setting should you use for the bridge configured as the root？（）

A.router（config-if）# speed basic-1.0 2.0 5.5 6.0 9.0 11.0 12.0 18.0 24.0 36.0 48.0 54.0
B.router（config-if）# speed 1.0 2.0 5.5 6.0 9.0 basic-11.0 12.0 basic-18.0 24.0 36.0 48.0 54.0
C.router（config-if）# speed basic-1.0 2.0 5.5 basic-6.0 9.0 11.0 12.0 18.0 24.0 36.0 48.0 54.0
D.router（config-if）# speed 1.0 2.0 5.5 basic-6.0 9.0 11.0 12.0 18.0 24.0 36.0 48.0 54.0

A.enable concatenation on the non-root bridge only
B.enable concatenation on the root bridge only
C.enable concatenation on both the root bridge and non-root bridge
D.enable concatenation on the root bridge and set it as desirable on the non-root bridge
E.set concatenation as desirable on the root bridge and enable it on the non-root bridge

A.x.509 certificate
B.generic token card
C.pre shared key
D.protected access credential