Which statement about Software Maintenance Upgrade is true？（）

• A、CRS-1 SMU can be applied to a different platform， and vice versa
• B、SMU is an executable code for running a process or libraries that are shared between the different processes
• C、SMUs for each release are individually downloadable from Cisco.com and come in the form of a tar ball
• D、SMUs provide software fixes for critical network down and qualification blocking issues Therefore，every software defect has a corresponding SMU
• E、SMUs are release-specific. If an issue affects multiple platforms or releases，an SMU is built separately for each release and each platform