"Chiếc đồng hồ hoàn hảo."
Translation:The watch is perfect.
I think what you are hearing is the back of the tongue with the C Sound going to the front of the tongue with the D sound. I am just learning some of the language but I hear this transition and have heard it in other sentences. The final consonant sounds almost silent to the English ear, but the tongue is still moving.
Who knows, it might depend on the context lol. I was wondering the same thing since that was the answer I gave. It said it was correct though.