Which of the Following Best Describes the Empirical Approach to Ethology

Which of the following best describes the empirical approach to ethology?

A) Always assume that correlations between two events indicate that one event caused the second event to occur.
B) Design controlled experiments in the field or laboratory.
C) Avoid manipulating ethological or environmental variables in order to conduct a properly controlled study.
D) Observe animal behavior in a natural setting to uncover interesting trends and use controls or manipulations to determine causality.
E) Utilize only observational methods to test theories and concepts related to animal behavior.