Which two statements are true about the logical storage…

Which two statements are true about the logical storage structure of an Oracle database?

A.
An extent contains data blocks that are always physically contiguous on disk.

B.
An extent can span multiple segments.

C.
Each data block always corresponds to one operating system block.

D.
It is possible to have tablespaces of different block sizes.

E.
A data block is the smallest unit of I/O in data files.