Jawaban:

1. Harry has just arrived home.
2. Your dad has not driven his car for ten days.
3. Alexander and Sarah have finished university this month.
4. Some of my best friends have come to my party.
5. Walter has never tasted Indian food.
6. My parents have flown to San Francisco twice.
7. Roger has understood the teacher's explanations.
8. Elizabeth has planted some new plants this morning.
9. They have already made their beds.
10. Uncle Patrick has smoked ten cigarettes today.
11. The farmer has milked all his cows this afternoon.
12. Katherine has helped her mom in the shop.
13. You have told me the funniest joke in your life.
14. The new mechanic has repaired my car this evening.
15. it's early so we haven't had breakfast yet.
16. Sheila has spent her holidays in Greece.
17. I have seen this American actress many times.
18. My youngest son has passed the final exams.
19. Richard and you have visited the Art Museum twice.
20. Have you ever been in Mexico?

Penjelasan:

The present perfect tense refers to an action or state that either occurred at an indefinite time in the past (e.g., we have talked before) or began in the past and continued to the present time (e.g., he has grown impatient over the last hour).

This tense is formed by:

have/has + the past participle