16. We ... for three hours when we saw the house in the distance.
a) drive c) drove
b) were driving d) had been driving
17. When they got outside, the rain ... already to snow.
a) turn c) has turned
b) had turned d) would turn
18. Agatha Christie ... at home. She didn't go to school.
a) has educated c) had educated
b) had been educated d) was educated
22. They ... across a field when they were attacked by a bull.
a) walked c) had been walking
b) have been walking d) were walking
23. He ... for a job for months, but he could find nothing.
a) looked c) had been looking
b) was looking d) has been looking
24. John felt tired. He ... all day to prepare for the party.
a) worked c) was working
b) had been working d) has been working