Amazon Neptune and Amazon DocumentDB are the correct choices for nonrelational engines to support graph and document data models on AWS.

Amazon Neptune is a managed graph database built for highly connected data and it supports both property graph and RDF models with Gremlin and SPARQL queries which makes it well suited for graph workloads such as relationship analysis and knowledge graphs.

Amazon DocumentDB is a managed document database that stores JSON like documents and it offers MongoDB compatible APIs which makes it appropriate for document oriented microservices and applications that use flexible JSON schemas.

Amazon RDS is a managed service for relational database engines such as MySQL PostgreSQL Oracle and SQL Server and it does not provide native document or graph capabilities so it does not meet the NoSQL requirement.

Amazon Aurora is a high performance relational database compatible with MySQL and PostgreSQL and it is optimized for transactional relational workloads rather than document or graph models.

AWS Storage Gateway is a hybrid cloud storage service that connects on premises environments to cloud storage and it is not a database so it does not satisfy the requirement for nonrelational engines.

Full AWS Practitioner Certification Question