Here are the correct answers for the blanks based on the context provided:

12. Art is a great form of **A. express** and allows people to express themselves creatively.

13. If **B. doesn't feel** like I will see a doctor.

14. It’s important to interact **C. with** different cultures to gain a broader understanding of the world.

15. If it rains tomorrow, I **B. stay** indoors and read a book.

16. I received an **A. invitation** to the party next week.

17. Would you like to participate **B. in** the charity walk with us?

18. She is always in a **C. hurry** in the morning to catch the train.

19. Learning a new language can be seen as a **B. method** of broadening your horizons.

20. Many people tend to spend more time on their phones than they realize. A **C. general** issue.

Feel free to ask if you have more questions!