Which three statements are true regarding the logical structure of the Oracle database? (Choose three.)
A.
It is possible to have tablespaces of different block sizes in a database.
B.
A data block is the smallest unit of I/O for data files.
C.
Multiple tablespaces can share single data file.
D.
Each data block in the database always corresponds to one OS block.
E.
Each segment contains one or more extents.