debt sustainability vs portfolio balance vs supply flow- PLEASE HELP

I keep getting questions wrong on this- seems to me like debt sustainability and portfolio balance are saying the same thing…higher fiscal deficits will lead to uncertainty from outsiders regarding ability to pay, which will devalue currency. Can someone clearly differentiate the three simply for me? Even reading it in the book im still confused how theyre all different. Thank you!!

There is an exact same question from CFAI online practice questions.

really? like in the discussions section on the study portal?