Which two statements are true?

After performing a clean shut down of the database instance for maintenance, you mount the database and then execute a command to open the database:
SQL> ALTER DATABASE OPEN;
Which two statements are true? (Choose two.)

A.
Instance recovery is performed before opening the database

B.
All the online data files headers are checked for consistency

C.
The online redo log files and online data files are opened

D.
The path and existence of all the log file members are checked