Questions: An epidemic curve depicting a distribution of cases traceable to multiple sources of exposure is a: point source epidemic curve. propagated epidemic curve. case control study. descriptive study.

The answer is the second one: propagated epidemic curve.

Explanation for each option:

1. Point source epidemic curve: This type of curve typically shows a sharp rise and fall in the number of cases, indicating that all cases were exposed to the source over a relatively short period. It is not suitable for multiple sources of exposure.

2. Propagated epidemic curve: This curve shows a series of progressively taller peaks, each one an incubation period apart, indicating that the disease is spreading from person to person. This is the correct answer for a distribution of cases traceable to multiple sources of exposure.

3. Case control study: This is a type of observational study where two groups differing in outcome are identified and compared to find a causal factor. It is not an epidemic curve.

4. Descriptive study: This type of study aims to describe the characteristics of a population or phenomenon being studied. It is not specific to epidemic curves.

Summary: The correct answer is the second one: propagated epidemic curve. This type of curve is indicative of cases traceable to multiple sources of exposure, showing the spread of disease from person to person over time.