Your application requires you to store large amounts of semi-structured data. While the read operations are frequent, write operations are infrequent. Cost optimization is a major factor for your team. Which NoSQL database offering on GCP best suits your needs?

*Explanation:* Cloud Bigtable. A. Incorrect, Cloud Spanner is a relational database service and may be overkill for semi-structured data. B. Incorrect, Firestore in Native Mode is optimized for mobile and server development, which may not be cost-effective for infrequent writes. C. Incorrect, Firestore in Datastore Mode is designed for high availability but can be costly. D) Correct, Cloud Bigtable is optimized for large amounts of single-keyed data with infrequent writes and frequent reads. It is also cost-effective for this use case. E) Incorrect, Memorystore with Redis is an in-memory data store and not suitable for large amounts of persistent data.