1. She was devastated because she _(miss) the opportunity to meet her favorite author. 2. By the time I arrived, everyone (sit) down for dinner. 3. The ice on the lake was thick enough, so they (skate) all day long. 4. He (wait) for hours when he finally saw his friend's car approaching. 5. She regretted that she (promise) to help him move out as it took up her whole weekend. 6. They (talk) about their plans for the future before they realized how late it had become. 7. Before submitting the report, she (write) and revising it for several days. 8. When we got there, they (be) playing music in the background. 9. He felt guilty that he (break) his promise to call her every day while he was away. 10. After he (wait for an hour, he decided to leave without buying anything. 1. I have (travel) to over 20 countries in the past year. 2. She (dive) with sharks before, but it still scares her every time. 3. They (skate) together since they were kids and now compete professionally. 4. He (make) a delicious meal from scratch using fresh ingredients. 5. Despite his best efforts, he (begin) studying for the exam until the night before. 6. She not do) any exercise for some weeks and can feel the effects on her body. 7. We (know) each other for years and always enjoy catching up. 8. When she saw him at the party, she (already know) that something was different about him. 9. He (sell) his car last week and is now relying on public transportation. 10. The company (sell) millions of products worldwide since its launch.

Sure! Here are the sentences completed with the correct verb forms:

1. She was devastated because she had missed the opportunity to meet her favorite author.

2. By the time I arrived, everyone had sat down for dinner.

3. The ice on the lake was thick enough, so they skated all day long.

4. He had been waiting for hours when he finally saw his friend's car approaching.

5. She regretted that she had promised to help him move out as it took up her whole weekend.

6. They had been talking about their plans for the future before they realized how late it had become.

7. Before submitting the report, she had been writing and revising it for several days.

8. When we got there, they were playing music in the background.

9. He felt guilty that he had broken his promise to call her every day while he was away.

10. After he had waited for an hour, he decided to leave without buying anything.

11. I have traveled to over 20 countries in the past year.

12. She had dived with sharks before, but it still scares her every time.

13. They have skated together since they were kids and now compete professionally.

14. He made a delicious meal from scratch using fresh ingredients.

15. Despite his best efforts, he did not begin studying for the exam until the night before.

16. She has not done any exercise for some weeks and can feel the effects on her body.

17. We have known each other for years and always enjoy catching up.

18. When she saw him at the party, she had already known that something was different about him.

19. He sold his car last week and is now relying on public transportation.

20. The company has sold millions of products worldwide since its launch.

Feel free to ask if you need any more help!