iCake, you gave the correct answer: Accusative and that is OK.
As for questions method, you confuse people. Reading the text with explanation and being unable to understand is very confusing and sometimes even painful.
And this kind of confusion is very common both on this forum and in general. Even during the time you are here there were several questions and discussions about case questions in different threads on this forum.
Think about that: what those questions are used for? To identify the case, right? You ask the question and the form of the question gives you a hint about the case if you learned that school table of questions vs case. But how do you know which exactly question to ask? You know it automatically because you are a native speaker. Foreigners don't know it automatically. That is obvious, one should not be an intellectual giant to figure it out by oneself. And one should not be a genius to come across one of those many discussions about case questions and remember a conclusion. You did neither of those and I feel useful to give you a hint either it looks polite or not.