In an AEM as a Cloud Service environment, a client needs a feature to be able to explicitly clear a dispatcher cache of required resources. Which approach is preferred to create this feature?

In an AEM as a Cloud Service environment, the preferred approach to clear dispatcher cache of required resources is to use the Replication API along with a replication flush agent. This method allows for programmatic clearing of the cache and is the standard way of invalidating cached content so that the dispatcher can retrieve fresh content from the publish instance.
Option A, "Enable the explicit cache invalidation feature in cloud manager," is not a standard feature available in Cloud Manager.
Option C, "Create a servlet, which will make an HTTP request to the dispatcher," is not advisable as it bypasses the recommended AEM replication and flushing mechanisms and could lead to inconsistencies.