Answer: the contents of a new textbook
Explanation:
The topic that is best suited for a formal discussion is the contents of a new textbook. This is suited to the formal discussion as it relates to educational settings such as a school.
Other options such as the weekend plans of your friends, the best places to shop online for new shoes and the best cookbooks for learning to make Thai food are all informal.
All of a sudden
Next time if you have choices you should include them in your question so it will be easier to help.
Answer:
to be absent tonight ...........
By avoiding sentimentality C--APEX