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.