I know that he did the work- বাক্যটির সঠিক পরিবর্তিত voice কি হবে?

1. কক) It was known to me that the work has been done by him.
2. খখ) It was known to me that the work had been done by him.
3. গগ) It was known to me that the work was done by him.
4. ঘঘ) It is known to me that the work was done by him.✓