Which ACID property ensures that transactions maintain consistency in the database?

The correct option is Consistency. Consistency in ACID properties ensures that transactions maintain the correctness and integrity of the database. It guarantees that any transaction brings the database from one valid state to another valid state, preserving data consistency despite concurrent transactions or system failures. Consistency ensures that database constraints are not violated, such as primary key uniqueness or referential integrity, maintaining the overall reliability of the database. This property plays a vital role in ensuring data accuracy and reliability in multi-user and high-transaction environments, preventing conflicting or erroneous data changes.