This is a negative risk (threat): the manufacturer may be unable to deliver due to financial trouble, which could delay the project or increase cost. The scenario already indicates the response: "the servers will be sourced from another vendor." That is best described as risk avoidance-changing the plan to eliminate exposure to the threatened vendor failure by not depending on that manufacturer. CompTIA Project+ includes performing risk management activities such as selecting risk management strategies and executing contingency/fallback plans.
"Mitigate" would mean reducing probability/impact while still accepting some exposure (e.g., adding schedule buffer, placing partial orders early, or increasing inspections), but here the team is switching vendors, which removes the root threat from the current plan. "Share" and "exploit" are typically associated with positive risks/opportunities, not threats, and don't fit a supplier distress scenario.
So the correct strategy is Avoid: replace the risky supplier dependency with an alternate sourcing approach to prevent the risk from materializing into a project issue (late delivery, non-delivery, or contract disruption).

Regression testing is a type of testing that is done on an existing system to ensure that the previous
functionality still works after a change has been made. Regression testing is a process of retesting or verifying
that a software system or application still performs as expected after it has been modified or updated with new
features, bug fixes, patches, etc. Regression testing can help to detect any errors or defects that may have been
introduced by the change and ensure that no functionality has been broken or degraded.

The project scope is the document that defines and describes the project objectives, deliverables, requirements, boundaries, assumptions, and constraints. It also includes the success criteria that should be fulfilled by the product or service to meet the stakeholder expectations and the business case. The success criteria are the measurable standards that indicate whether the project has achieved its intended results. The other options are not correct because:
A quality plan is the document that defines and describes the quality standards, policies, procedures, tools, and techniques that will be applied to the project to ensure that the deliverables meet the requirements and the success criteria.
Contract obligations are the terms and conditions that bind the parties involved in a contractual agreement, such as the project manager, the customer, the sponsor, and the vendor. Contract obligations specify the roles, responsibilities, deliverables, payments, and penalties of each party.
A work breakdown structure (WBS) is a graphical representation of the project scope that breaks down the deliverables into smaller and manageable components. A WBS shows the hierarchy and relationship of the project elements, but does not include the success criteria. Reference = CompTIA Project+ Study Guide: Exam PK0-005, 3rd Edition, Chapter 6: Planning Projects, Part 2 (Scope, Quality, and Risk), pages 175-179; CompTIA Project+ Certification Exam Objectives, Domain 2: Project Planning, Objective 2.1: Given a scenario, create a project charter and project management plan.

The project manager should have prepared acceptable communication channels to avoid the situation of a stakeholder not replying to emails due to intermittent Internet service. Acceptable communication channels are methods or modes of communication that are agreed upon by all parties involved in a project. They may include aspects such as email, phone call, text message, video conference, instant message, or face-to-face meeting. Acceptable communication channels can help to ensure that messages are delivered and received effectively and efficiently and that communication preferences and limitations are respected.

An RFP (request for proposal) is a document that solicits proposals from potential vendors for a specific
project or service. An RFP typically describes the project scope, requirements, evaluation criteria, and
instructions for submitting proposals. An RFP is the best document for the company to use to obtain and
compare information on cabling services and costs from various vendors, as it allows the company to evaluate
the vendors' qualifications, experience, approach, and pricing12.