Which two statements regarding the IS-IS DIS election process are true？ （）

A priority of 0 will prevent a router from becoming a DI
B. If the DIS becomes unavailable the backup DIS is promoted to DI
C. Adding a router with a higher priority than the current DIS will result in the new router becoming DI
D. Separate L1 and L2 election processes are held on a brodcast network.
E. L1 routers on a broadcast network only establish adjacencies with the DI
F. If there is a tie based on priority，the router whose attached interface has the lowest MAC address becomes the DI