Which operation is used to update a document in a MongoDB collection?

The operation used to update a document in a MongoDB collection is known as "UPDATE." This command allows for modifying existing documents by specifying the criteria for which documents should be modified and the modifications to be applied.

In MongoDB, the UPDATE operation can be performed using either the updateOne() or updateMany() methods. The updateOne() method updates a single document that matches the specified condition, while updateMany() allows for updating all documents that match the criteria. The operation can also include various update operators, such as $set, to modify specific fields within the documents without replacing the entire document.

Using "UPDATE" is essential for maintaining or changing data within a collection while preserving aspects of the documents that should remain unchanged, making it a powerful and flexible operation in data management within MongoDB. Other options, while related to updating or modifying data in different contexts, do not specifically represent the MongoDB command for updating documents in a collection.