The correct answer is B, because a product Increment does not have to be released to production at the end of each Sprint. The Scrum Guide states that "at the end of a Sprint, the new Increment must be 'Done,' which means it must be in useable condition and meet the Scrum Team's definition of 'Done'. An increment is a body of inspectable, done work that supports empiricism at the end of the Sprint. The increment is a step toward a vision or goal." Therefore, a product Increment must be potentially releasable, but the decision to release it is up to the Product Owner.

The best answer is B. The need for the team to learn based on doing work and measuring results.
The Sprint length should be chosen based on the complexity and volatility of the product and the environment, as well as the team's capability and Definition of Done. The Sprint length should enable the team to deliver a usable Increment of value that meets the feedback needs of the stakeholders and the business. The Sprint length should also allow the team to inspect and adapt their work processes and practices based on the outcomes of the Sprint.
The other options are not valid reasons for choosing the Sprint length. The organization's mandate, team formation, and release schedule should not dictate the Sprint length, but rather be aligned with it. The Scrum Team should have the autonomy to choose the Sprint length that best suits their product and context.
You can learn more about how to choose the right Sprint length from these sources: How Long A Sprint Should Be?, How to Choose the Right Sprint Length in Scrum, What is a Sprint?, Determining the Sprint Length, and Sprint Length: What's the Right Length?.

The correct answer is B, because the Sprint Backlog is created during the Sprint Planning meeting. The Scrum Guide states that "the Sprint Backlog is the set of Product Backlog items selected for the Sprint, plus a plan for delivering the product Increment and realizing the Sprint Goal."

The Product Backlog is ordered by the Product Owner with the most valuable items placed at the top, as stated in [6]: "The Product Owner is responsible for ordering items on their product backlog based on their value to customers and users. Value can be measured by various factors, such as business value, customer satisfaction, risk reduction, learning opportunities, etc. The most valuable items are placed at the top of the product backlog so that they can be delivered sooner by the development team."

According to the Scrum Guide1, the Sprint Review is an informal meeting at the end of the Sprint, where the Scrum Team and stakeholders collaborate about what was done in the Sprint. Based on that and any changes to the Product Backlog during the Sprint, attendees collaborate on what to do next. The Product Owner explains what Product Backlog items have been "Done" and what has not been "Done"; the Development Team discusses what went well during the Sprint, what problems it ran into, and how those problems were solved; and the Development Team demonstrates the work that it has "Done" and answers questions about the Increment. The entire group collaborates on what to do next, so that the Sprint Review provides valuable input to subsequent Sprint Planning. The Sprint Review is mainly an inspect and adapt opportunity for the Scrum Team and stakeholders.