1)Epidemiology is:

A)Part of the nursing process for community health nurses.

B)Used to examine the incidence of communicable diseases.

C)Used to understand and explain how and why health and illness occur.

D)Important in determining the prevalence of chronic diseases.

C.      Used to understand and explain how and why health and illness occur.

Step-by-step explanation

Epidemiology refers to the study of determinants and distribution of events and states related to health among different populations such people in schools, cities, and even states. Therefore,  it is used to understand and explain how and why health and illness occur among different groups of people or regions. Therefore, C is the correct answer.