Which commands is used to assign executable permission to all of the files named “letter”? A. chmod ugo+r letter B. chmod ugo+rw letter C. chmod u+x letter D. chmod ugo+x letter E. None of the above

The correct answer is D. chmod ugo+x letter.

The chmod command is used to change the permissions of a file. The u, g, and o stand for user, group, and other, respectively. The + sign means to add permissions, and the x permission means that the file is executable. So, chmod ugo+x letter will add executable permission to the file letter for the user, group, and other.

Option A, chmod ugo+r letter, would add read permission to the file letter for the user, group, and other.

Option B, chmod ugo+rw letter, would add read and write permission to the file letter for the user, group, and other.

Option C, chmod u+x letter, would add executable permission to the file letter for the user.

Option E, None of the above, is incorrect because it does not match the question.