Clusters of Disease Can Be Challenging to Investigate Because

Multiple Choice

Clusters of disease can be challenging to investigate because:

A) Cases of disease can occur close together (geographically or in time) just by chance
B) They are usually caused by environmental hazards
C) The exposure and disease usually occur very close together
D) The disease usually only has a single cause
E) All of the above
F) Noneoftheabove