Companycom would like the ability to shrink filesystems. They currently have JFS filesystems. Which of the following is necessary to shrink the filesystems?（）

• A、Copy the existing filesystems to JFS2
• B、Defragment the filesystem， then reduce its size
• C、Change the file system attribute allow_shrink=yes on the existing filesystems
• D、Modify the logical volume attribute allow_shrink=yes on the existing logical volumes