A researcher is examining potential risk factors in comparison with disease at a specific time through collecting data regarding current exercise, sleep patterns, and current health status among 12-year-olds. Which research study would be most appropriate?

Correct Answer: A

Rationale: By definition, a cross-sectional study examines relationships between potential causal factors and disease at a specific time. A prospective study monitors a group of disease-free individuals to determine if and when disease occurs. A retrospective study compares individuals with a particular condition or disease with those who do not have the disease. A true experiment involves both an experimental group who receives an intervention and a control group who does not receive an intervention.

Correct Answer: A

Rationale: Endemic (A) describes a disease consistently present at a stable level in a population (e.g., malaria in some regions). B is an epidemic, C an emerging disease, and D eradication.

Correct Answer: B

Rationale: Case fatality rate (B) measures severity as deaths among cases (e.g., Ebola). A is new cases, C is total cases, D is deaths broadly.

Correct Answer: D

Rationale: RCTs (D) are experimental, not observational. A, B, and C observe natural events without intervention.

Correct Answer: B

Rationale: Outbreak investigation (B) identifies sources (e.g., Snow’s pump) for control. A, C, and D are secondary or unrelated.