? 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
原文：http://blog.51cto.com/13854012/2151103