25、Which is true about logical and physical database structures? (Choose the best answer)
A. An undo tablespace has a temp file instead of a data file.
B. A segment can consist of extents of different sizes.
C. A permanent tablespace can only contain tables segments and index segments.
D. A tablespace can consist of data blocks of different sizes.
E. An extent always consists of physically contiguous data blocks in storage.
Correct Answer: B