The statistics for a poorly performing， dual-processor x365 system are as follows： （1）Processor： 80% for 5-second increments （2）Memory page faults： 360/second average over 15 minutes （3）Disk % disk time： 100% Which of the following will provide the greatest performance improvement？（）
- AAdd memory
- BAdd a processor
- CExchange the existing processor for a faster processor
- DAdd a faster disk subsystem