1. There is/there are
2. Prepositions of place
3. Possessive adjectives
4. Pronouns this/these, that/ those

1. nobody (knew) where smith (had gone). 2. a girl who (was standing  ) under the beech tree (came) up to us. 3. mary (was speaking) to mr boxwell when i (saw) her in the corridor this morning. 4. john (was  parking) the car in fifth avenue when a young man in black glasses (appeared) from nowhere and (stood) before him. 5. he again (came) to the village where he (had lived) in childhood. 6. while we (were talking), there (came) a loud knock at the door. 7. he (looked) into the drawing-room. the old man (was  sleeping) peacefully in the armchair at the fire-place. 8. when their visitor (left) john and his mother (stood) near the window. 9. when he (dresssd), he (went) downstairs, (wrote) a long letter to his parents and another to his sister. 10. she (welcomed) her with a bright smile and (turned) back to the offensive dandy lions she (had been  fighting) with. 11. while she (was  reading) this notice, a middle-aged woman (appeared) in the doorway. 12. when he (came) back to the conference room, he (saw)  that the situation (had  changed). 13. she (had been  sitting) at the table only five minutes when a car (came). 14. their father (was) still silent, even when they (had) coffee. 15.the three (sat) down to the meal that susan (had  prepared). 16. he (was sitting)  thinking of his wife whom he (had  left) alone in europe. 17. they (looked) over the accounts together and (found) where she (had  made) her mistake. 18. i (was  ) surprised at john's failure because he (had been) such a good student previously.