The correct answer is A. atomicity.
Atomicity is a property of database transactions that ensures that either all of the changes made by a transaction are committed, or none of them are. This means that a transaction cannot be partially committed, and that it cannot be rolled back without affecting all of the changes that it made.
Consistency is a property of database transactions that ensures that the database is always in a consistent state, even if a transaction fails. This means that if a transaction is rolled back, the database will be restored to the state it was in before the transaction started.
Isolation is a property of database transactions that ensures that the changes made by one transaction are not visible to other transactions until the first transaction has been committed. This prevents transactions from interfering with each other.
Durability is a property of database transactions that ensures that the changes made by a committed transaction are permanent, even if there is a system failure. This means that if a database crashes after a transaction has been committed, the changes made by the transaction will be restored when the database is restarted.
In conclusion, atomicity is the property of database transactions that ensures that either all of the changes made by a transaction are committed, or none of them are.