Which command is used to delete all files in the current directory as well as all files and sub-directories in its subdirectories? A. rm * B. rm -r * C. rm all D. rm *.* E. None of the above

The correct answer is: B. rm -r *

The rm command is used to delete files. The -r option tells rm to delete directories recursively, meaning that it will delete the directory and all of its contents. The * wildcard matches any file or directory name. So, the command rm -r * will delete all files and directories in the current directory, as well as all files and directories in its subdirectories.

Option A, rm *, would delete all files in the current directory, but it would not delete any directories. Option C, rm all, is not a valid command. Option D, rm *.*, would delete all files in the current directory, including hidden files. Option E, None of the above, is also incorrect.