Which of the following describes a transient error when invoking a remote service?

A transient error when invoking a remote service refers to an issue that is typically temporary and can resolve itself without any changes to the underlying system or application. The correct choice describes a situation where the service is running on a system that is temporarily unavailable. This could occur due to various reasons, such as network issues, system maintenance, or server overload. Since it is not a persistent error, the connection to the remote service may be restored after a short period, making it an example of a transient error.

In contrast, a misunderstanding of the request format indicates a more persistent issue relating to the interface's expectation rather than a temporary fault. Sending the request to the wrong system is also a permanent configuration problem, ultimately needing a change in the request's direction. Incorrect calculation of returned order totals hints at a logic error in the service itself, rather than a transient condition affecting availability. Each of these alternatives presents scenarios that reflect issues with service integration but do not embody the transient nature of the service being temporarily unavailable.