What must be passed through the options for every method in a transaction?

The session object is essential for managing transactions in MongoDB. When executing a transaction, the session object is used to group operations together and enables the system to maintain the ACID (Atomicity, Consistency, Isolation, Durability) properties. Each transaction must be initiated within a session, allowing the database to track the operations and ensure they are either committed or aborted together. This is crucial for maintaining data integrity during multi-document transactions.

Without passing the session object in the options for methods involved in the transaction, the database cannot recognize that the operations belong to a particular transaction context, potentially leading to inconsistencies and undesired outcomes in the database state. Thus, ensuring that the session object is included is a mandatory aspect of executing transactions in MongoDB.

In contrast, while the database name, write concern, and timeout duration can be relevant for various operations in MongoDB, they are not specifically required for defining the boundaries and behaviors of transactions as the session object is.