You executed the following commands in a database session: 
What could have caused the recycle bin to clean up?
A. There is demand for space from the new table
B. The undo tablespace does not have sufficient free space
C. The new table name is the same as the table name in the recycle bin
D. The temporary tablespace that is assigned to you does not have sufficient free space
原文：http://www.cnblogs.com/Babylon/p/7843519.html