28. At 7 a.m. I ______ breakfast. What were you doing? a) ate b) eat c) am eating d) was eating

was eating — вопрос “What were you doing?” задаёт контекст продолжающегося действия в прошлом.

At 7 a.m. I was eating breakfast. What were you doing? (В семь утра я завтракал. Что ты делал?)