2. At the conference, I --- the professor who --- about ancient civilizations. a. saw – was talking; b. was seeing – talked; c. was seeing – was talking; d. saw – talked

Перевод задания: Выберите правильные варианты.

a. saw – was talking. At the conference, I saw the professor who was talking about ancient civilizations. (На конференции я увидел профессора, который рассказывал о древних цивилизациях.)

Встреча с профессором — завершённое событие (Past Simple), а его речь — продолжавшееся действие (Past Continuous).