That's an easy one :)
Question particles fall into two categories, dependent and
independent. Most are independent and followed by the relative
pronoun. The tricky bit is that usually is subsumed by the vowel but
re-appears when a word gets in between:
cò (a) tha seo?
cò fon ghrèin *a* tha seo?
dè tha seo?
dè fon ghrèin a tha seo?
ciamar a tha sibh?
carson a tha sibh...?
cuin a tha sibh...?
Then there's the dependent one, mainly càit. In the present tense it
looks like it has the relative particle but it's actually the
interrogative particle, as you can see in the past tense:
càit a bheil...
càit an robh
Am Mìcheal Eile