Exercise 1

2. decided

3. flown

4. gone

5. heard

6. kept

7. made

8. ridden

9. seen

10. swum

11. traveled

12. worked

Exercise 2

2. 've ridden

3. 've heard

4. 've seen

5. 's flown

6. 've swum

7. 's decided

8. 's worked

Exercise 3

2. have appeared

3. have...loved

4. have not stopped

5. has researched

6. (has) written

7. have... received

8. has described

9. has found

10. has promised

11.have not become

12. have increased

13. has continued

14. has ...encouraged

15. have not read

Exercise 4

2. How many times have you visited

    I’ve visited Europe more than 10 times 

3. Have you ever been

    I’ve recently been on an African safari

4. Have you ever been

    Yes, I’ve been to Costa Rica

5. How often have you been

    I’ve been there once

6. Have you (ever) traveled

    No, I’ve never traveled in China

7. Have you ever gone up

    No, I’ve never gone up in a hot-air balloon

8. Have you ever swum

    I’ve swum with dolphins many times (OR six or more  times)

9. Have you ever taken

    No, I’ve never taken a group tour

Exercise 5

2. Q: been everà ever been

3. Q: 've returnedàreturned

4. Q: staysà stayed

A: several times stayed thereà stayed there several times

5. A: tookà taken

6. Q: hasà have   

    chooseàchosen

A: booked justàjust booked 

    wasàbeen