којих

којих

"Којих" means "of which" or "of whom" in English.

Relates to the pictures discussed previously, serves as a relative pronoun connecting the subject pictures with the discussion.

Видео сам слике о којих смо разговарали.

I saw the pictures about which we talked.

Part of the phrase 'којих питања', modifying the noun 'листа' to specify it by its questions.

Листа којих питања је најважнија?

Which list of questions is the most important?

Functional as a pronoun describing the friends, indicating characteristics (their number) in a descriptive clause.

Пријатељи, којих је било много, су помогли.

The friends, of whom there were many, helped.