The following design (see attached diagram) uses third-party REST APIs that are publicly available through...

VSAP Open Connectors is the most appropriate capability for replacing "1" in the diagram, as it enables seamless integration with third-party REST APIs.

Why SAP Open Connectors?

Provides pre-built connectors for third-party REST APIs, ensuring easier integration with publicly available APIs over the internet.

Includes features like authentication, API abstraction, and unified access to multiple non-SAP services.

Other Options:

B (SAP Cloud Connector): Used for secure connectivity between SAP BTP and on-premise systems, not for public REST APIs.

C (SAP Business Connector): Legacy solution for integrating SAP and non-SAP systems, not ideal for REST API integration.

D (SAP Connectivity Service): Provides general network connectivity but lacks the specific API management and abstraction features of Open Connectors.

References:

SAP Open Connectors Overview