Place it immediately after the unbelievable claim in your edit, so it answers the setup directly. Follow it with the Oh My God Wow sound for a bigger reaction, or lead into it with Sudden Suspense when you want the claim to land harder before the reply.
关于此声音
This is a short spoken reaction clip, lasting about three and a half seconds, in which a voice delivers the line 'You can not be serious' with clear disbelief. It feels incredulous and exasperated, like a direct challenge to something that sounds completely wrong. The tone is blunt and comic, making it easy to recognise as a quick dismissal of an unbelievable claim.