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In this instance, dirty reads are disallowed, while nonrepeatable reads and phantom reads are allowed.

  • A.Read committed
  • B.Read uncommitted
  • C.Repeatable read
  • D.Serializable

Answer: A

Correct answer: Read committed

Read committed guarantees only that data read has been committed by someone, so dirty reads are impossible. It takes no long-term read locks, so a row may change between two reads within the same transaction - a non-repeatable read - and new rows may appear, a phantom. It is the default level in most systems, as a compromise between correctness and concurrency.

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