An internal source of recruitment is:

Recruitment sources are broadly categorized as internal (within the organization) or external (outside the organization). The question asks for an internal source.

• Promotion from within (D) is the correct answer. This method involves filling a job vacancy by promoting an existing employee to a higher-level position. It is a classic example of internal recruitment, leveraging the current workforce's skills and experience.
• Job portals (A) are incorrect. These are online platforms (e.g., Indeed, LinkedIn) used to advertise jobs to a wide audience outside the company, making them external recruitment sources.
• Campus placements (B) are incorrect. This method involves recruiting students directly from educational institutions, which are external entities to the organization.
• Employee referrals (internal) (C) is incorrect in this context. While the referral *program* might be internal, the candidates referred by employees are typically external to the organization, making it an external recruitment method. The question specifically asks for a source where the candidate is already *within* the organization.