Ex 16.
1. has lived
2. lived
3. has stopped
4. stopped
5. has bought
6. bought
7. has blew off
8. has changed
9. changed
10. traveled
Ex 18.
1. Why has he stopped?
2. is looking. . . . hasn't found
3. has been
4. What are you studying now?
5. have given
6. is knitting
7. You have only had a piece of cake.
8. are planting
9. Are you going to plant tomatoes this year.?
10. have found. . . gave. . .