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