Refer to the exhibit. The sequence diagram shows a RESTful API call. Which step and response will represent the behavior of the REST API call to be synchronous?

A POST that returns immediately when a slot is available provides only a creation acknowledgment, not the finished result - this is the trigger step of an asynchronous flow.

A GET request to /discovery/ that returns only when the discovery operation is fully finished is synchronous because the client blocks until the complete result is available in the response body. This contrasts with asynchronous patterns where the initial call returns immediately with a reference ID and the client must poll separately. The GET verb retrieving a completed resource state is the hallmark of a synchronous interaction.

Receiving a response when the discovery is merely created (not finished) means the client must poll later for the result, which is the definition of asynchronous behavior.

PUT is used to update a resource, not to retrieve a completed discovery result; this does not represent a synchronous retrieval of the final outcome.