Final answer:
Both the Supervisory Appraiser and Trainee Appraiser are responsible for the improperly documented experience log.
Step-by-step explanation:
The responsible party for the improperly documented experience log in the scenario described is D) Both the Supervisory Appraiser and Trainee Appraiser jointly.
The Trainee Appraiser is responsible for properly documenting their experience log, as it is part of their role and requirement to submit accurate records to the Appraisal Board. However, the Supervisory Appraiser also has a shared responsibility to ensure that the trainee's log is properly documented and meets the required standards set by the Board.
When the Board reviews the log and determines it to be improperly documented, it implies that both parties, the Supervisory Appraiser and the Trainee Appraiser, did not fulfill their respective responsibilities in maintaining proper documentation.