While Mary ... (have) dinner, she ... (read) the news; what ... (happen) that day.
was having / was reading / had happened
How many books ... (you / read) before you ... (take) the exam?
had you read / took
She ..... (realize) only at the airport that she ..... (leave) her passport at home.
realized / had left
When I ... (get) home, the guests ... (leave) and the children ... (sleep).
got / had left / were sleeping
What ... (you / do) while I ... (cook) the meal?
were you doing / was cooking