C. Defined staffing needs is the best answer because an organization cannot develop an effective sourcing strategy until it knows what talent it needs to obtain. Sourcing decisions—including where to search, which candidate populations to target, what employment message to communicate, which channels to use, and how much recruiting capacity is necessary—must be based on clearly identified workforce requirements.

The HRCI SPHR Exam Content Outline places this question within Functional Area 02: Talent Planning and Acquisition . It first requires HR to evaluate and forecast organizational needs to develop workforce plans and then requires the development of recruitment strategies, including “sourcing and branding strategy.” This sequence is important: workforce demand informs sourcing.

Defined staffing needs typically address the number of employees required, job or capability requirements, critical skills, timing, geographical requirements, employment arrangements, and expected future demand. CIPD workforce-planning guidance likewise describes workforce planning as determining future workforce needs and identifying gaps between current supply and future demand. Recruitment guidance similarly emphasizes understanding the skills required for current and future organizational performance before recruiting.

A. Focused benchmarking can provide useful comparative information about competitors, labor markets, recruiting practices, or staffing metrics, but benchmarking is an input rather than the foundation of the sourcing strategy.

B. Environmental scanning helps HR understand external conditions such as labor availability, economic conditions, demographic changes, competitors, and technological trends. It can shape a sourcing strategy but does not define exactly what talent the organization needs.

D. Cost-benefit analysis helps compare recruiting channels or evaluate whether particular sourcing investments are worthwhile. However, HR cannot effectively evaluate costs and benefits until staffing requirements have been established.

The logical SPHR sequence is determine workforce demand first, then select sourcing methods capable of meeting that demand . Without defined staffing needs, recruiting activity may generate many applicants while failing to produce the particular capabilities required by the business.

Therefore, C is the strongest answer.