If I learnt Belarusian, I would read a Belarusian book.

A. I were learning to Belarusian, I could read a Belarusian book.

B. Were I to learn Belarusian, I would read a Belarusian book.

C. Were I learning to Belarusian, I would have read a Belarusian book.

D. Had I learnt Belarusian, I would have read a Belarusian book.