If a Participant Has a Missing Value on an Item

If a participant has a missing value on an item that is part of a multi-item measure (such as 1 item not answered on a 20-item depression questionnaire) , the researcher might handle this by:

A) substituting that person's average on the items that were completed
B) substituting a similar person's score on that item
C) substituting the total score on the questionnaire for that item
D) all of the above are viable options