Questions & Answers about Che cosa studi con l'insegnante?
Why use che cosa instead of just cosa to say 'what'?
How do we know who is studying if there is no word for 'you'?
The verb ending gives it away. Studi comes from the regular verb studiare (to study). The -i at the end tells us it is the tu (informal 'you') form. Italian usually drops the subject pronoun because the verb does the work for you.
Why does l'insegnante have an apostrophe?