The project manager should ask an experienced team member to coach the new team member, as this is a strategy for developing the skills and performance of the new team member. According to the PMI website, coaching is one of the interpersonal and team skills that a project manager should have. Coaching is a process of providing guidance, feedback, and support to help someone improve their abilities and achieve their goals.
By asking an experienced team member to coach the new team member, the project manager can leverage the knowledge and expertise of the existing team, and foster a culture of learning and collaboration. The project manager can also monitor the progress and results of the coaching, and provide recognition and rewards to both the coach and the coachee.
The other options, asking the new team member to follow the team ground rules, asking an experienced team member to identify a replacement, or asking the new team member to reassess their own capabilities, are not the best ways to deal with a new team member who is not making the expected progress on an assigned task.
Asking the new team member to follow the team ground rules may help the new team member to understand the expectations and norms of the team, but it does not address the specific issues or challenges that the new team member is facing. Asking an experienced team member to identify a replacement may be a drastic and demotivating measure, that may not be feasible or fair to the new team member. Asking the new team member to reassess their own capabilities may be a constructive feedback, but it does not provide any support or assistance to the new team member.
References: 1 Interpersonal and Team Skills - Project Management Institute 2 A Guide to the Project Management Body of Knowledge (PMBOKGuide) - Sixth Edition, Chapter 9.4.2.4 3 Business Analysis for Practitioners: A Practice Guide, Chapter 5.3.3