"He is asking our mother."
Translation:Ptá se naší matky.
I've noticed in this exercise we are using the singular genitive form of matka. However, in a previous exercise, "They are asking about our sister" was translated as "Ptají se na naši sestru" where "sestru" is singular accusative. When would it be appropriate to use the genitive vs. the accusative in two very similar sentences? Is it active vs. passive? And is there a list of which verbs require the genitive vs. accusative? Thanks for any help!