It should be yn, but because chi ends with a vowel, you take away the y and put in the ' to show there is a letter missing.
It sounds to me like "Dych chi'n hoffi'r brecwast?" Does anyone else hear the "r" on the end of "hoffi"?
I didn't. Sometimes I completely miss the r though, I think it's one of those things that is said super fast and runs into the other words. Sometimes I listen to the slow mode. That helps.
What does the presence, or lack thereof, of 'n signify?
I believe it's a shortened form of 'yn'. (Don't quote me on any of this) I think it's dych chi yn hoffi, but they abbreviate the chi and yn to chi'n.
Why is chi'n never sounded in this kind of exercise? We need practice hearing what it sounds like every time.