J'ai du gateau. C'est pour le dessert. Il est pour le dessert. Which is correct?
The way I understand this is that "pour le dessert" is a prepositional phrase functioning as an adverbial phrase. When you have an adverbial phrase with "être" and you are referring specifically to something which has been mentioned you use "il est", "elle est", etc. As an example we have: Où est le livre. "Il est sous la chaise." and not "C'est sous la chaise."
Here the specific referent is "du gâteau" and I would think that you use "Il est pour le dessert" and not "C'est" and yet "C'est pour le dessert" seems to be the correct response. Why is this the case?