Which essential public health service involves diagnosing and investigating health problems and hazards?

The essential public health service that involves diagnosing and investigating health problems and hazards is accurately identified as 'B'. This service is crucial in identifying outbreaks, understanding the dynamics of health issues, and determining the causes of health-related events or diseases in communities. By investigating health problems and hazards, public health professionals can gather the necessary data to inform decision-making and develop strategies to mitigate risks, ultimately leading to improved health outcomes for the population.

This service encompasses a range of activities, such as surveillance of disease trends, conducting epidemiological investigations, and responding to public health emergencies. This proactive approach allows health officials to identify disparities and patterns in health conditions, which is essential for effective health promotion and disease prevention efforts. By diagnosing and investigating, public health agencies can focus their resources strategically, ensuring timely interventions and effective health policies.