Which option is true when calculating round-trip delay in IP SLA operations？（）

A、The processing time on the end routers is only assessed for operations that involve the responder.

B、The processing time on the end routers is only assessed for operations that involve the transmitter.

C、The processing time on the end routers is only assessed for operations that involve both the responder and the transmitter.

D、The processing time on the end routers is not assessed for neither the responder nor the transmitter.