关于CIO（cellIndividualOffset），以下哪组参数的选择，更有利于解决A3切换的拐角效应问题？ | About cellIndividualOffset (CIO), Which configuration can improve the Event-A3 handover performance at the street corner.
A.服务小区CIO = 1| CIO OF SERVING CELL IS 1
B.邻区CIO = -1 | CIO OF NEIGHOR IS -1.
C.服务小区CIO = -1 | CIO OF SERVING CELL IS -1
D.邻区CIO = -1 | CIO OF NEIGHOR IS -1.
正确答案是BC