The correct answer is Core SQL API.

Core SQL API is designed to store and query JSON documents and it exposes a SQL like query language that you can use to filter, project, and aggregate JSON data. It supports automatic indexing of JSON properties and familiar SQL style syntax so you can run SELECT FROM WHERE and JOIN queries across document collections.

MongoDB API is for applications that use the MongoDB wire protocol and the Mongo query language. It stores BSON or JSON like documents but you would use Mongo query operators rather than the SQL like language provided by the SQL API.

Gremlin graph API is intended for graph data models and traversals. It uses the Gremlin traversal language and is optimized for nodes and edges so it is not appropriate for SQL style queries over JSON documents.

Cassandra API implements a wide column model compatible with Cassandra and uses CQL. It is focused on table like and wide column data rather than document oriented SQL queries, so it is not the right choice for JSON document queries.

Full AWS Practitioner Certification Question