Does scrum require retrospective and sprint burndown?

Hi,

I'm new to this forum, and obviously have a question while preparing for PSPO1: I stumbled upon the question:

Which of the following is required by Scrum?
A) Sprint Retrospective
B) Members must stand up at the Daily Scrum
C) Sprint Burndown Chart
D) Release Planning
E) All of the above

So, my assumption is, that answer B is correct, as I read it already.
What I'd like to know: Is sprint retrospective AND sprint burndown chart really strictly required? I always thought it is a recommentation to have one, but no strict rule, is my assumption correct?
Not sure if answer D is correct, I thought we always talk about PB and SB, but not about release plan, or did I misinterpret it?

I hope you can help? Thanks in advance.
Cheers
Reni