This is the best option because it allows the project manager to address the current and future needs of the project, while also developing the skills and knowledge of the team. According to Project Management Best Practices for 2024 + Expert Tips, one of the best practices is to "provide your team members with opportunities to learn new skills and grow professionally". This can increase their motivation, engagement, and productivity, as well as reduce turnover and improve quality.
Option A is not the best option because it may create conflicts or dependencies with another team, and it does not solve the long-term need for an SME in the specific area.
Option C is not the best option because it may incur additional costs and risks, and it does not foster the development of the team.
Option D is not the best option because it does not address the issue at all, and it may delay the project progress and quality.