Detailed Explanation:

Answer: Option 1 — Certifying the skills acquired by construction workers through traditional channels.

The Recognition of Prior Learning (RPL) Scheme is a key component of the Pradhan Mantri Kaushal Vikas Yojana (PMKVY). It aims to certify and recognize the skills acquired by workers through informal or non-formal means, particularly those gained through work experience rather than formal training. The scheme is particularly relevant for construction workers, domestic workers, and others in the unorganized sector who have learned skills through traditional channels or on-the-job experience. RPL provides them with formal certification aligned to the National Skills Qualification Framework (NSQF), enhancing their employability and enabling them to access better opportunities. The scheme does not focus on distance learning enrollment (Option 2), job reservation in PSUs (Option 3), or certifying trainees under formal NSDP programs (Option 4), as those who complete formal training receive regular certification.