Which tags are not closed in HTML?

Related questions

1. What is the HTML code structure?
2. Is HR a self closing tag?
3. What is an HR director?
4. Is HR Business Partner higher than HR manager?
5. What are the types of HTML tag?
6. What is the difference between P and BR?
7. What is the difference between an HR manager and an HR director?
8. What does br /> do?
9. What is the difference between HR and BR in HTML?
10. What is HR executive salary?

Tags

1. #would
2. #however
3. #because
4. #colgroup
5. #tbody
6. #without
7. #option
8. #these
9. #thead
10. #implied
11. #closing
12. #started
13. #tfoot
14. #optional
15. #following