Interrogative pronouns are used to ask questions. “What?” and “Who?” have cases based on there location in the sentence. For example you would use the prepositional to ask “About what?”. Example: “What are you talking about (О чём вы говорите?)” .
What?
| English | What |
| Nominative Case | Что |
| Accusative Case | Что |
| Genitive Case | Чего |
| Dative Case | Чему |
| Instrumental Case | Чем |
| Prepositional Case | Чём |
Who?
| English | Who |
| Nominative Case | Кто |
| Accusative Case | Кого |
| Genitive Case | Кого |
| Dative Case | Кому |
| Instrumental Case | Кем |
| Prepositional Case | о Ком |