A consultant has been asked to do a performance analysis on a database server.  Which subsystem should the consultant first analyze and why？（）

• A、CPU，because the database replication process requires a considerable amount of CPU time
• B、Memory，because the buffer cache requires a large amount of memory to maintain the data in system memory
• C、Disk，because it is important to configure a sufficient number of disks to match the CPU processing power
• D、Network，because the data returned to the client from the server can be a large subset of the total database