The correct answer is A. Md.
The command md is used to create a new directory. It is short for “make directory”. The syntax is md directory_name. For example, to create a new directory called “new_directory”, you would type md new_directory.
The command cd is used to change the current directory. The syntax is cd directory_name. For example, to change to the directory called “new_directory”, you would type cd new_directory.
The command rd is used to remove a directory. The syntax is rd directory_name. For example, to remove the directory called “new_directory”, you would type rd new_directory.
The command none of above is not a valid command.