Correct Answer: D - Establishing a Cloud Interconnect connection between the on-premises data center and Google Cloud, followed by using the Storage Transfer Service, is the most efficient and secure method. Cloud Interconnect provides a dedicated, high-throughput, low-latency connection, ensuring secure and efficient data transfer. The Storage Transfer Service automates and simplifies the process, making it ideal for transferring large amounts of data quickly.

Why the other options are incorrect:

• A: Manually handling encryption, decryption, and verification with a Transfer Appliance is time-consuming and inefficient for transferring 1 PB of data within a few hours.
• B: A Cloud VPN connection with parallel gcloud compute scp jobs lacks the performance and security of Cloud Interconnect and Storage Transfer Service.
• C: Breaking the data into 3 TB batches and using gsutil may not meet the tight timeframe, and checksums for each batch could further delay the process.