Structured Streaming achieves end-to-end fault tolerance through Checkpointing and Idempotent Sinks.

• Checkpointing saves the current state of the streaming query, including input stream offsets, allowing the query to restart from the last checkpoint after a failure, ensuring no data loss.
• Idempotent Sinks can process the same data multiple times without duplicating results, ensuring consistency even if data is reprocessed due to failures or retries.

Other options are incorrect because:

• Watermarking manages late data and triggers micro-batch processing but doesn't directly aid in fault tolerance.
• Write-ahead logging, while useful in some systems, isn't a primary fault tolerance mechanism in Structured Streaming.
• Failover to available nodes is part of fault tolerance but doesn't alone ensure data consistency or prevent loss without checkpointing and idempotent sinks.