3.
2. has visited
3. have not understood
4. has he opened
5. have eaten
6. have you seen
7. has not invited
8. have the boys finished
9. has changed
10. have not listened
4.
2. have they seen a snake? --------Yes, they have
3. has she met someone famous?--------No, she hasn`t
4. has he ridden a horse?------No, he hasn`t
5. have you had a toothache?----Yes, I have
6. have they been late before?-----Yes, they have