Answer: gsutil for the migration; Pub/Sub and Dataflow for the real-time updates

The correct answer is **C**. - **gsutil for the migration**: `gsutil` is a command-line tool that allows you to manage Cloud Storage resources. It is a reliable and efficient tool for transferring large files to Google Cloud Storage. Given the files are large (90 GB each), `gsutil` is a suitable choice for this task. - **Pub/Sub and Dataflow for the real-time updates**: - **Pub/Sub**: Cloud Pub/Sub is a messaging service that enables you to send and receive messages between independent applications. It can be used to stream real-time updates from your transactional systems to your data warehouse on Google Cloud. - **Dataflow**: Cloud Dataflow is a fully managed service for processing and enriching real-time data streams. It offers a scalable and reliable way to process and analyze streaming data, ensuring your transactional systems continually update the warehouse on Google Cloud in real time. **Why the other options are incorrect**: - **A**: BigQuery Data Transfer Service is not suitable for migrating data from an on-premises data center to Google Cloud Storage. Dataproc, while capable of real-time data processing, is not as well-suited for streaming data processing as Dataflow. - **B**: While `gsutil` is appropriate for the initial data migration, it is not designed for real-time updates. Pub/Sub and Dataflow are better suited for this purpose. - **D**: Storage Transfer Service is primarily for transferring data from on-premises storage to Cloud Storage and is unnecessary in this scenario. Cloud Data Fusion can be used for real-time data processing, but Dataflow is more appropriate for continuously updating a data warehouse in real time.

Author: LeetQuiz Editorial Team