Final answer:
Root cause investigation is the essential element of an occupational safety and health program that identifies the underlying reasons for incidents to prevent them.
Step-by-step explanation:
The core element of an effective occupational safety and health program that identifies root causes and helps prevent incidents is B) Root cause investigation. The root cause investigation process involves analyzing incidents to determine the underlying causes. For example, 4.17 illustrates a safety engineer conducting an investigation by examining accident reports to find instances where accidents were caused by employees not following instructions. This process helps in understanding why an incident occurred and in implementing measures to prevent future occurrences.