Normal distributions are an important concept to researchers because ______.

A) there is only one normal distribution
B) they do not actually exist
C) they are the basis of statistical techniques used by researchers
D) they help define 'normal' and 'abnormal' behavior

Normal distributions are the basis of many statistical techniques used by researchers, including hypothesis testing, confidence intervals, and regression analysis. They allow researchers to make assumptions about the probability of certain outcomes or events, and to draw conclusions based on data analysis. While normal distributions can be used to define 'normal' and 'abnormal' behavior in some contexts, this is not their primary function in research.