In the Relational Model, what is the primary purpose of a 'Candidate Key' that is not chosen as the Primary Key?

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Data warehouses are designed to support strategic decision-making through integrated and historical data. Reason (R): Data warehouses primarily process day-to-day operational transactions in real time. In the light of the above statements, choose the most appropriate answer from the options given below:

Match LIST-I with LIST-II regarding NoSQL database types and their built-in primary indexing mechanisms: LIST-I (NoSQL Database Type) A. Key-Value Store B. Document Database C. Column-Family Store D. Graph Database LIST-II (Primary Indexing Mechanism) I. Partition key (hash) plus clustering columns II. Node labels with relationship types III. Hash-based index (O(1) lookup) IV. _id field (primary B-tree index) Choose the correct answer from the options given below: