OCP 1Z0 052 21

21. Which three statements are true about logical structures of the Oracle database? (Choose three.) 
A.Each segment contains one or more extents.  
B.Multiple tablespaces can share a single data file. 
C.A data block is the smallest unit of input/output (I/O) in data files.  
D.It is possible to have tablespaces of different block sizes in a database.  
E.Each data block in the database always corresponds to one operating system block.  
Answer: ACD

B 不对，应该是一个表空间可以包含多个数据文件。一个数据文件只能属于一个表空间
E data block 与 os block的倍数，而不是一对一