单项选择题
YouareusingstandaloneCiscoAironet1400SeriesWirelessBridgesforanine－milepoint－to－point wirelesslinkbetweentwobuildings.Whichdistancesettingshouldyouuseforthebridgeconfiguredasthe root？（）
A.20km[12.4miles]
B.10km[6.2miles]
C.5km[3.1miles]
D.25km[15.5miles]
E.15km[9.3miles]