Which option is true when calculating round-trip delay in IP SLA operations？（）
- AThe processing time on the end routers is only assessed for operations that involve the responder.
- BThe processing time on the end routers is only assessed for operations that involve the transmitter.
- CThe processing time on the end routers is only assessed for operations that involve both the responder and the transmitter.
- DThe processing time on the end routers is not assessed for neither the responder nor the transmitter.