What does the SCN represent？（）  

A The system change number， which is a point in time relative to transactions within a given database.

B A number that represents time. Thus， at 1300 hours， the SCN is the same on all databases. 

C The security change number， which represents the security code that is needed to access any database structure.

D A conversion factor that converts internal database time to external clock time.

E UTC time in the database，providing a standardized way of tracking time in Oracle.