Why has she fallen ___ love with such an old man? Вопрос 12Ответ a. with b. on c. in d. __

It seems like you're asking about prepositions in Russian. The correct preposition to use in this context is "in." Therefore, the correct answer to the question is "c. in" – "в."

When describing falling in love in Russian, we use the preposition "в" followed by the accusative case. This structure illustrates the idea of someone falling into the emotional state of being in love.

If you have any more questions about language or grammar, feel free to ask for further clarification!