AB+DF+CD+BC
=AB+BC+CD+ DF
=AF．
故答案为：AF．
28 He spoke very slowly, but he still didn’t get his meaning _______.
A across B cross C through D though
在开放式基金开放申购、赎回后，投资者可以申请办理转托管，但存在( )等情形不能申请转托管。
A．风险警示
B．质押
C．冻结
D．待处理
