3 ..... Spanish for a long time?

Analysis:

The question asks about a duration of time concerning learning Spanish. The correct question form to inquire about past actions over a period is 'Have you been studying'.

Breakdown:

• A Do you study: Incorrect. This is present simple, asking about a general habit.
• B You studied: Incorrect. This is past simple, asking about a completed action.
• C Have you been studying: Correct. This is present perfect continuous, used to ask about an action that started in the past and continues up to the present or has recently stopped.

Translated Question:

3 ..... ты испанский долгое время?