Which of the following are not required by Scrum?

Which of the following are not required by Scrum?
A . Using User Stories.
B. Have a Product Owner.
C. Answering the "three questions" in the Daily Scrums.
D. Having time boxed Scrum Events.
E. Have a Sprint Backlog.
F. Using the concept of Story Points.

Answer: A,C,F

Explanation:

It is not mandatory in Scrum to use User Stories, Story Points and to answer the "three questions", but it is a common way and recommended to do so.