The Product Backlog and the Definition of "Done" are artifacts that promote transparency.

Explanation
The Product Owner is responsible for maximizing the value of the product resulting from the work of the Scrum Team1. One of the ways to do this is to order the Product Backlog in a way that reflects the flow of value to the stakeholders and customers2. The Product Owner can use various factors to order the Product Backlog, such as value, risk, dependencies, learning opportunities, and feedback loops3.
However, sometimes the Product Owner may face challenges or constraints that affect the ordering of the Product Backlog, such as external dependencies, market changes, technical issues, or stakeholder requests4. In such cases, the Product Owner needs to balance between delivering value and managing risks. The Product Owner may need to adjust the Product Backlog ordering to account for these factors, but not at the expense of compromising the value delivery5.
In this scenario, the Developers are waiting for an external supplier to deliver a specific product component that they need to integrate and use. Without that component there will not be enough work in the next Sprint to occupy the full team. They ask their Product Owner to re-order the Product Backlog. The Product Owner asks the Scrum Master for help. A good advice for the Product Owner would be to tell them that their primary concern is the flow of value reflected in the ordering of the Product Backlog. Timeline of the flow might be influenced by such dependencies and require some level of Product Backlog re-ordering.
This advice would help the Product Owner to focus on delivering value while also considering the impact of the external dependency. The Product Owner could work with the Developers and stakeholders to identify and prioritize other valuable work that can be done in the next Sprint without relying on the external component.
The Product Owner could also communicate with the external supplier and try to minimize or eliminate the dependency as much as possible.
The other options are not good advice for the Product Owner. Telling them that they need to re-order the Product Backlog to maximize utilization of the Developers would imply that keeping productivity high is more important than delivering value. This would go against the Scrum values of focus and respect. Telling them to remove all work involving the external component from the Product Backlog and create a new backlog for it would imply that they are ignoring or avoiding the dependency rather than managing it. This would go against the Scrum values of courage and openness.
References:
The Scrum Guide 2020, section "The Product Owner"
What is a Product Backlog?| Scrum.org, section "Ordering"
Product Backlog Ordering - Zen Ex Machina, section "Ordering by Value"
Product Backlog Ordering - Zen Ex Machina, section "Ordering by Risk"
Ordered Not Prioritized | Scrum.org, section "Ordering by Dependencies"
[The Scrum Values | Scrum.org], section "The Scrum Values"

Explanation
This is a good option because the Scrum Master's role is to help the Scrum Team understand and apply the Scrum framework and its principles12. The Scrum Master should also facilitate and enable the team's self-organization and collaboration12. By coaching the Scrum Team, the Scrum Master can help them realize that the Daily Scrum is not a status update or a performance review, but a time to inspect and adapt their progress toward the Sprint Goal3.
D) Tell the Product Owner your concerns about how his behavior may impact the Developers, and ask him to stop attending the Daily Scrum for some time.
This is another good option because the Scrum Master's role is to protect the Scrum Team from external interference and distractions12. The Scrum Master should also coach the Product Owner on how to maximize the value of the product and collaborate effectively with the Developers12. By telling the Product Owner your concerns, you can help him understand that his behavior may create pressure, dependency, or resentment among the Developers, which can harm their motivation, creativity, and autonomy . By asking him to stop attending the Daily Scrum for some time, you can give the Developers some space to self-manage their work and communication.
References: 1: What is a Scrum Master? | Scrum.org 2: What is a scrum master? [+ Responsibilities] | Atlassian 3: What's the role of the Product Owner at the Daily Scrum? | by Maarten Dalmijn | Serious Scrum | Medium : Scrum Guide | Scrum Guides : Product Owner's Role in a Daily Scrum: How to Support the ... - Eleken : The Power of Intrinsic Motivation - Forbes

For a single product there is one Product Backlog. For a single Product Backlog there is one Product Owner.