Oraciones en present perfecto en ingles?

1. - Scientist have discovered a new cure for the disease.

2. - I’ve played that game before, I don’t like it.

3. - He has developed a fine taste in wine.

4. - The boss has already been informed.

5. - I have worked for the company before.

6. - She has been cooking all morning.

7. - Have you checked this data before printing?

8. - They have been off and on the relationship for months.

9. - I have seen what he can do.

10. - I have taught this game to all of my friends.