The purpose of foreign keys is to: Uniquely and universally identify instances of the class into which they are posted. Link relations so the database can be used to store business data and to generate useful information. Create null values in the database. Determine minimum multiplicities of associations between classes. Determine maximum multiplicities of associations between classes QUESTION6 Which level of the REA enterprise ontology is based specifically on the business-entrepreneur script? Value system Value chain Business process Task None of the above