III.1 of

2 in

3 at... on

4 about

5 to...by

6 in

7 of

8 at

9 in

10 in

IV. 1 younger

2 as old

3 most beautiful

4 bigger

5 more difficult

6 as comfortable

7 most powerful

8 better 

9 as slowly

10 happier

V.1 hasn't been returned yet by Mary

2. is smaller than her house

3 difficult to find a job at my age

4 is older than Mai

5 was sent to school by my parents when I was six years old

6 easy to get acquainted with the regulation in a new school

7 is more expensive than a bicycle

8 isn't written by rhe principal

9 harmful to your health

10 is being made in the kitchen by Mary