Which two statements regarding the IS-IS DIS election process are true？ （）
- AA priority of 0 will prevent a router from becoming a DIS.
- BIf the DIS becomes unavailable the backup DIS is promoted to DIS.
- CAdding a router with a higher priority than the current DIS will result in the new router becoming DIS.
- DSeparate L1 and L2 election processes are held on a brodcast network.
- EL1 routers on a broadcast network only establish adjacencies with the DIS.
- FIf there is a tie based on priority，the router whose attached interface has the lowest MAC address becomes the DIS.