The statistics for a poorly performing x366 system are as follows：      （1）Processor： 90% for 5 second increments   （2）Memory page faults： 20/second average over 15 minutes      （3）Disk： disk time 1%  Which of the following will provide the greatest performance improvement？（）

• A、Add memory
• B、Add a processor
• C、Add a faster disk subsystem
• D、Exchange the processor with a faster processor