Which of the following methods can enforce data consistency in Access?

Defining clear relationships between tables is crucial for enforcing data consistency in Access. By establishing relationships, you create rules that govern how data in one table relates to data in another. This helps maintain referential integrity, which ensures that references between tables remain valid. For example, if you have a primary key in one table and a foreign key in another, Access can prevent actions that would lead to orphaned records—where a record refers to a non-existent entry in another table.

Clear relationships allow Access to enforce constraints such as cascading updates and deletions, meaning if you update or delete information in a primary table, related records in other tables can be automatically updated or removed as well. This prevents inconsistencies that might arise from manual entry or poor data handling, thus maintaining the accuracy and reliability of the database.

Other methods mentioned, such as using graphs to visualize data trends or setting up automatic updates from external databases, while useful for reporting or integrating data, do not inherently enforce or maintain data consistency within the database structure itself. Multiple entries per field could lead to confusion and data redundancy, which violates the principles of data integrity.