The most effective action the Project Manager can suggest to ensure the most effective collaboration of the Solution Development Team is:

C. Relocate these employees to a new project area, with a number of desks where the Solution Development Team can sit together.

Co-locating team members in a shared space is a well-established practice in Agile environments to enhance communication, collaboration, and team dynamics. By having the Solution Development Team sit together, the Project Manager can facilitate more efficient face-to-face interactions, quick resolution of issues, and a better sense of team unity. This approach leverages the benefits of immediate communication and collaborative problem-solving, which are key in Agile project management. Even though the team members are currently in the same office, their separation into different ends of the office could hinder spontaneous communication and collaboration. Creating a dedicated project area for the team can significantly improve their ability to work together effectively.