From where should a connector be invoked to fetch currency exchange rates from an external system?

The correct choice highlights that the most appropriate place to invoke a connector for fetching currency exchange rates from an external system is through the integrator shape in a flow. This is because the integrator shape is specifically designed for handling calls to external systems, facilitating seamless interaction with APIs or web services to retrieve data.

Invoking a connector in a flow using the integrator shape allows for a streamlined process where the data retrieval fits naturally within the workflow. It ensures that the flow can continue to operate normally while waiting for a response from the external system, thus enhancing efficiency and maintaining user experience. This shape incorporates error handling and response processing, making it well-suited for such tasks.

In contrast, the other options may not offer the same level of integration with external systems or workflow management. For instance, invoking a connector from a flow action would not provide the same direct context or handling mechanisms as an integrator shape. Data pages are more suitable for accessing and managing data already present within the application rather than initiating external calls. Lastly, while activities can certainly make connector calls, they tend not to be as visually integrated within the flow as the integrator shape, which could potentially lead to more complex flow management and error handling scenarios.