中国大学MOOC: A _________ is a document that certifies the nationality of its holder for international travel.

Peer Assessors and the Candidate are asked to sign the Peer Assessment form because：________.（ ） A: It makes the form look more official. B: The professor should sign the form. C: It certifies that the assessment has been done according to the rules. D: The Assessment Form can be sent to the student’s parents. E: A signed Assessment Form is required by the university career centre.