How Can I access Mac OS X Base System on Boot Screen? Im going to try to wipe out my hard drive and reinstall Mavericks but whenever i reboot the iMac and hit the OPTION key it won't show Mac OS X Base System. Can anyone help me on this?
If you mean the Recovery HD, then it means that you don't have a Recovery HD that's able to be booted into.

Try booting with ⌘R. If that fails, use ⌘⌥R for Internet Recovery.