What is a slang word for "inactive", "lazy", "abnormally slow-thinking"?
Please look at this situation.
A friend (A) is teaching English to his friend (B). B is usually dynamic and cheerful but the class today is going on very badly, B is answering reluctantly, he hardly ever smiles. He looks as if he is obsessed in some unpleasant thoughts. Or maybe just tired. B has to pull out answers from him all the time. Finally A asks him: "Come on, B, wake up, why are you so ________ today? Something happened?"
What slang word may be put in here?