1. came, was cooking, was working
2. were choosing, saw, was speaking
3. was writing
4. dusted, vacuumed
5. turned off, locked
6. returned, were sleeping
7. got, left
8. What were you doing when I phoned you yesterday? — I was preparing for the English exam
9. Where was Mike riding when you met him yesterday afternoon? — He was riding to the post-office
10. When did your sister finished reading this book? — She read it all day yesterday and finished late in the evening