"Where are you, Morag?"
Translation:Càite a bheil thu, a Mhòrag?
I'm not sure how that works. If it was an older person you respected, but nevertheless address then by their Christian name? Maybe someone will explain. (My students were allowed to call me Morag rather than Dr Kerr, but would they nevertheless have been expected to address me as sibh if we had been speaking in Gaelic? I'd have thought so.)
The query on the response "Càite a bheil thu, a Mhòrag?" was why "sibh" as an answer was rejected. An error which has probably been dealt with since reported.
The "càit" and "càite" dilemma was (for me anyway) dealt with on a different question.......and I think that too has been dealt with.
Two of the answers in this part of the course are càite a bheil thu? where are you? and ciamar a tha thu? how are you?.
Why do the two questions use different forms of to be, bheil and tha?
Càite and ciamar are both question words, so that's the same.
Is it that how are you? expects an answer with an adjective such as I'm good, whereas where are you? expects a noun phrase with preposition, such as I'm in Portree ?
Or is just a rule we have to learn that where takes the bheil forms and how the tha forms?
That's a good question and a good suggestion. It could be that you had to use different verbs to answer the two questions and so you need different verbs in the questions. This would happen with a 'Who are you?' question. You use Is in the answer so you can't use Tha or bheil in the question.
But it isn't that here. You answer with the the same verb in both cases so both questions use the same verb. Just different parts of the verb. For some reason you are using the question form for one and the statement form for the other. Perhaps it was originally 'How [is it that] you are?' It's buried in the mists of time but I'm sure someone knows.
You basically nailed it with "how is it that you are?"
"... a tha thu ..." is a dependent clause, "Ciamar" is a contraction which I forget the full original form of, but notice "mar" which you'll have met (or will meet later) mean 'like' essentially. It's something along the lines of "what like is it that you are?"