What component is used to interact with external services in MuleSoft?

The correct choice is a connector, which is a fundamental component in MuleSoft used to establish connections with external services and systems. Connectors function as bridges that facilitate communication between Mule applications and various endpoints like databases, web services, messaging systems, or other APIs. They encapsulate the necessary protocols and authentication methods, making it easier for developers to integrate with external resources without needing to manage the underlying technical details.

Transformers, while important in MuleSoft for transforming data formats or structures, do not handle communications with external services directly. Models, typically used for structuring data or defining the data schema, also do not serve the purpose of connecting to external services directly. API specifications outline how APIs should behave and their contracts but do not perform the function of establishing a connection; instead, they guide the implementation of API endpoints. Thus, connectors are indeed the core components designed specifically for interacting with external systems in MuleSoft.