What does ACID stand for in databases?

• A. Accessibility, Consistency, Integrity, Durability
• B. Atomicity, Consistency, Isolation, Durability
• C. Atomicity, Concurrency, Isolation, Durability
• D. Accuracy, Consistency, Isolation, Durability

Answer: (B)

ACID defines four properties of database transactions to ensure reliable processing: Atomicity, Consistency, Isolation, Durability. Atomicity means a transaction is all-or-nothing—either every operation succeeds or none do, so partial changes aren’t applied. Consistency means a transaction brings the database from one valid state to another, preserving all integrity constraints and rules. Isolation ensures that concurrently running transactions don’t interfere with each other, so the final result is as if they happened in some serial order. Durability guarantees that once a transaction is committed, its effects are permanent even if the system crashes later.

The best answer uses the canonical terms Atomicity, Consistency, Isolation, and Durability. Other options swap in non-standard terms like Accessibility, Integrity, Concurrency, or Accuracy, which aren’t part of the ACID set.