Which of the Following Can Be Used for "Walling Off

Which of the following can be used for "walling off" an attorney from a case where a conflict of interest exists?

A) Using password protection for all files related to the case
B) Sending a memo to all employees that a certain lawyer should not have access to specific files
C) Flagging hard copies of files to indicate that they are restricted
D) All of these choices are correct.