正解:B
Reference:
The primary difference between synchronous and asynchronous APIs is how they handle responses. Synchronous API calls wait for the server to process the request and return a response immediately. In contrast, asynchronous API calls do not wait for the server to complete processing; instead, they allow the client to continue executing other tasks, and the response is returned later, typically via a callback or polling mechanism.
Cisco DevNet Associate Study Guide: Understanding API Types (Chapter 7, Section: Synchronous vs Asynchronous APIs).