Which three statements about STP timers are true？（）

A. STP timers values （hello， forward delay， max age） are included in each BPD
B. A switch is not concerned about its local configuration of the STP timers values. It will only consider the value of the STP timers contained in the BPDU it is receiving.
C. To successfully exchange BPDUs between two switches， their STP timers value （hello， forward delay， max age） must be the same.
D. If any STP timer value （hello， forward delay， max age） needs to be changed， it should at least be changed on the root bridge and backup root bridge.
E. On a switched network with a small network diameter， the STP hello timer can be tuned to a lower value to decrease the load on the switch CP
F. The root bridge passes the timer information in BPDUs to all routers in the Layer 3 configuration.