Not able to load QuestionResponse as part of candidatejobapplication.dat

Content (required):

Getting an error while loading candidatejobapplication.dat HDL file - "The line for component QuestionResponse with instruction MERGE doesn't include values that define a unique reference to the record."

Can someone provide some light on why this error message even though I am providing QuestionCode, QstnVersionNum, AnswerCode in the HDL file. It's a response based on question code hence I did not provide any value for QuestionnaireCode, QstnrVersionNum

Version (include the version you are using, if applicable):

Rel 13, 21C

Code Snippet (add any code snippets that support your topic, if applicable):

METADATA|CandidateJobApplication|CandidateNumber|RequisitionNumber|CategoryCode|ConfirmedByCandidateNumber|SubmissionConfirmedDate|InactivateFlag|CurrentPhaseCode|RejectionReasonCode|RejectionReasonComments|ReturnToPriorPhaseFlag|ReturnToPriorStateFlag|Source|SourceMedium|CurrentStateCode|SubmissionLanguageCode