Which two statements correctly describe the relationship between data files and logical database structures? (Choose two.) 

Answer options:

A. A segment cannot span data files.
B. A data file can belong to only one tablespace.
C. An extent cannot span data files.
D. The size of an Oracle data block in a data file should be the same as the size of an OS block.

BC

A single extent can never span data files. https://docs.oracle.com/database/121/CNCPT/logical.htm#CNCPT1095