The people who will perform the work make the final estimates.

The Scrum Master is responsible for serving the team by facilitating and removing impediments to ensure there are minimal roadblocks in the way of the team. The Scrum Master also coaches the Scrum Team and organization to ensure the benefits of Scrum is realized.
"Removing every impediment for the Development Team" may seem like the right thing to do but by doing it this way, the Dev Team's ability to self-organize would be limited. There are some impediments that will depend solely on the Scrum Master and there will be some that require collaboration with the Dev Team. The former might be working with the finance department to renew services that the team is using. The latter might be lack of skills to make a particular item done. The Scrum Master can coach the team on finding different solutions to resolve the issue.
"Removing impediments" is good. "Removing every impediment for the Development Team" is not so good and sometimes not even possible.

The Scrum Master is responsible for promoting and supporting Scrum as defined in the Scrum Guide.
Scrum Masters do this by helping everyone understand Scrum theory, practices, rules, and values.
The Scrum Master is a servant-leader for the Scrum Team. The Scrum Master helps the Scrum Team understand which of their interactions are helpful and which aren't.
The Scrum Master helps everyone change these interactions to maximize the value created by the Scrum Team.

Explanation
The Product Owner is responsible for maximizing the value of the product and the work of the Developers.
The Product Owner is also accountable for managing the Product Backlog, which is an ordered list of what is needed in the product. The Product Owner should collaborate with the Developers and the stakeholders to create and refine the Product Backlog, as well as to define and communicate the product vision and goals.
Therefore, as a Scrum Master, you should direct the new Product Owner towards focusing on:
Building a good relationship with the stakeholders of the product (A), which is a valid option as it helps the Product Owner to understand and align with the changing organizational or market expectations, as well as to invite and receive feedback from the appropriate stakeholders during the Sprint Review, which is an event that inspects the outcome of the Sprint and determines future adaptations.
Relying on others in the Scrum Team and the stakeholders to formulate the Product Backlog (D), which is another valid option as it helps the Product Owner to leverage the functional and business insights of the Developers and the stakeholders, who are more familiar with the product and the customer needs. By questioning them and working with them, the Product Owner will quickly become more productive and effective.
The other options are not correct because they:
Inform the Product Owner that it is important that the Developers are updated on changing business priorities on a daily basis at the Daily Scrum (B), which is not a good option as it shows a misunderstanding of the purpose and format of the Daily Scrum, which is an event for the Developers to inspect their progress and plan their work for the next 24 hours, not a status report or a meeting for changing requirements or scope. The Product Owner should respect and support the Developers' commitment to their Sprint Goal and Sprint Backlog, and only introduce changes that do not endanger them.
Tell the Product Owner to make sure that there are no ambiguities or possible misunderstandings in the items on the Product Backlog by capturing the functional requirements during an analysis phase, which is not a good option as it shows a misunderstanding of the nature and process of the Product Backlog, which is a dynamic and emergent artifact that can change as more is learned about the product, users, market, and technology. The Product Owner should collaborate with the Developers to refine and clarify the Product Backlog items throughout the product development, not create detailed documents that are considered as final outputs of analysis Sprints.
References: : [Scrum Guide], The Product Owner : [Scrum Guide], The Product Backlog : [Scrum Guide], The Sprint Review : [Scrum Guide], The Scrum Master : [Scrum Guide], The Developers : [Scrum Guide], The Daily Scrum

Scrum employs an iterative, incremental approach to optimize predictability and control risk. The primary objective of a Sprint (iteration) is to produce a potentially shippable product Increment.
Having an Increment will allow the Scrum Team to know the right thing to do in the upcoming Sprint. Having a velocity is important but working software is the primary measure of progress.