Wh-questions
From Scottish Gaelic Grammar Wiki
Wh-question (Adger and Ramchand 2005:(12))
Cò a bha sgith? who C.REL be.PST tired 'Who was tired?'
Equative wh-question when the subject is a wh-element ((Adger and Ramchand 2005:(15))
Cò an tidsear? who the teacher 'Who is the teacher?'
Pied-piped wh-question (Adger and Ramchand 2005:(21))
Dè an seòrsa tidsear a tha annad? what the sort teacher C.REL is in + you 'What sort of teacher are you?'
Fronted wh-phrases are always nominative marked (Adger and Ramchand 2005:(31)).
Dè a' chraobh a bha thu a'geàrradh? which the tree.NOM C.REL be.PST you cutting 'Which tree were you cutting?'
The sentence becomes ungrammatical with genietive marking on the noun inside the wh-phrase (Adger and Ramchand 2005:(31)),
Dè a' chraobhe a bha thu a'geàrradh? which the tree.GEN C.REL be.PST you cutting 'Which tree were you cutting?'
although the object noun is marked with genitive in declaratives (Adger and Ramchand 2005:(30))
Bha thu a'geàrradh na craoibhe. be.PST you cutting the tree.GEN 'You were cutting the tree.'