You need a managed MongoDB service with an SLA for an application running on GKE. What should you do?

Deploying MongoDB Atlas from the Google Cloud Marketplace is the correct choice because it provides a fully managed MongoDB service with an SLA, directly integrated with Google Cloud. This option simplifies deployment, scaling, and maintenance, ensuring high availability and reliability for your application. Creating a Cloud Bigtable cluster is incorrect because Bigtable is a NoSQL wide-column store, not a document database like MongoDB, and it doesn't offer a native MongoDB API. Installing MongoDB manually on Compute Engine instances or a Managed Instance Group is incorrect because these approaches require significant operational overhead for management, patching, backups, and high availability, and they do not inherently come with an SLA for the database service itself.