Which of the following describe the process identifier that is used to run OSPF on a router?（）
- A It is logically significant.
- B It is globally significant.
- C It is needed to identify a unique instance of an OSPF database.
- D It is an optional parameter required only if multiple OSPF processes are running on the router.
- E All routers in the same OSPF area must have the same process ID if they are to exchange routing information.