Which command is used to begin a transaction?

The command used to begin a transaction in MongoDB is withTransaction(). This method is part of the MongoDB Node.js driver and provides a convenient way to carry out transactions in a session. When using withTransaction(), you can specify a function that contains the operations you want to execute as part of the transaction. This ensures that all operations within the function get executed as a single atomic unit, meaning that either all operations are applied if successful, or none are if an error occurs.

Utilizing withTransaction() also helps simplify the code needed to handle transaction logic, as it automatically manages the session and other transaction states for the developer. It takes care of starting the transaction and also addresses the complexities involved with transaction management, such as committing or aborting the transaction based on the success or failure of the operations executed within the specified function.

The other options listed represent commands that are not part of the MongoDB transaction API, which reinforces why withTransaction() is the correct choice. The absence of proper methods like startTransaction(), beginTransaction(), or initTransaction() in MongoDB’s documentation and API further emphasizes that the framework only recognizes withTransaction() for managing transactions effectively.