You must know 25 basic concepts of C #

Let's review the questions in C # below. Can you answer them? The answer will be published later !!!
1. What are the differences between static and non-static variables?
2. What is the difference between const and static readonly?
3. What does extern mean?
4. What does abstract mean?
5. What is the role of the Internal modifier?
6. What is the sealed modifier?
7. What is the difference between override and overload?
8. What is an index indicator?
9. What is the role of the new modifier?
10. What is the meaning of this keyword?
11. Can I use Abstract Functions to override virtual functions in the base class?
12. Can there be virtual functions in the seal class?
13. If there is only one attribute accessor for the virtual attribute in the base class, how many attribute accessors can be created after the inherited class overrides this attribute? What if the base class contains get and set?
14. can abstract be used with virtual? Can it be used with override?
15. What members can an interface contain?
16. What is the difference between classes and structures?
17. What problems does interface multi-inheritance bring about?
18. What is the difference between an abstract class and an interface?
19. What is an alias indicator?
20. How to release unmanaged resources?
21. P/invoke?
22. What is the difference between stringbuilder and string?
23. What is the meaning of explicit and implicit?
24. What is the use of Params?
25. What is reflection?