While I was reading a book, my brother __ video games. (played / was playing / plays)

Перевод задания: Пока я читал(а) книгу, мой брат играл в видеоигры.

was playing — длительное действие происходило одновременно с другим действием в прошлом.

While I was reading a book, my brother was playing video games. (Пока я читал(а) книгу, мой брат играл в видеоигры.)