A use case is a technique that describes how an actor interacts with a system to achieve a goal or perform a task. A use case consists of a main scenario and possible alternative scenarios that capture the normal, exceptional, and error flows of events. A use case can also include the acceptance criteria that specify the conditions that must be met for the use case to be successfully completed and accepted by the stakeholders.
The test team can review the use cases to help identify the acceptance criteria for the solution, as they provide a comprehensive and realistic view of the expected behavior and outcomes of the system. The test team can also use the use cases to design and execute test cases that verify and validate the functional requirements and acceptance criteria of the solution. References: PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline1, page 20; Business Analysis for Practitioners: A Practice Guide2, page 99.

Verification is the process of ensuring that the requirements meet a quality checklist and conform to the specified standards, rules, and criteria. Verification can help the business analyst to ensure that all requirements meet a quality checklist before the development and testing phase by checking the completeness, correctness, clarity, consistency, and testability of each requirement. Verification can also help to identify and resolve any defects, errors, or ambiguities in the requirements. References: = PMI Professional in Business Analysis (PMI-PBA)Examination Content Outline (2019), page 10; Business Analysis for Practitioners: A Practice Guide (2015), page 40.

A review of the solution prototype would be the most viable technique to use in this scenario for validating requirements through in-person sessions. A solution prototype is a simplified version of part or all of a solution that can be used to elicit feedback from stakeholders. A review of a solution prototype involves presenting or demonstrating it to stakeholders and asking them questions to assess their satisfaction, understanding, agreement, or concerns. A review of a solution prototype can help to validate that the solution meets the stakeholder requirements and delivers value to them. A brainstorming session is a technique for generating ideas or solutions by encouraging free and creative thinking from participants. A brainstorming session can help to elicit or analyze requirements but not validate them. A use-case development session is a technique for creating use cases that describe how actors interact with a system to achieve their goals. A use- case development session can help to elicit or specify requirements but not validate them. A review of the previous version is a technique for examining an existing solution or product to identify its strengths, weaknesses, opportunities, or threats. A review of the previous version can help to elicit or analyze requirements but not validate them. References: PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline1, page 13; Business Analysis for Practitioners: A Practice Guide2, page 76.

The business analyst should trace the requirements and measure the impact of the requested changes on the existing delivery date. Tracing the requirements means identifying the source, dependencies, and relationships of the requirements, and ensuring their alignment with the business needs, objectives, and expectations.
Measuring the impact of the changes means assessing how the changes will affect the scope, schedule, cost, quality, and risk of the project. These actions can help the business analyst and the project team to evaluate the feasibility and priority of the changes, and to communicate the implications and alternatives to the customer and other stakeholders. References: PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline1, page 23; Business Analysis for Practitioners: A Practice Guide2, page 131.

Customer metrics on the existing system are an input into solution evaluation and decision making in this context, as they provide a baseline for measuring the performance and value of the new solution. The business analyst can use these metrics to compare the existing system with the new solution and assess how well the new solution meets the customer needs and expectations. A cost-benefit analysis of the existing system is not an input into solution evaluation and decision making, as it does not reflect the customer perspective or satisfaction with the system. Technical readiness of the development team is not an input into solution evaluation and decision making, as it does not relate to the quality or effectiveness of the new solution. A new solution design specification is not an input into solution evaluation and decision making, as it describes how the new solution will be built, not how it will perform or deliver value. References: Business Analysis for Practitioners: A Practice Guide, page 176-177; PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline, page 20.