What Is the Difference Between Experimental and Nonexperimental Methods of Study

What is the difference between experimental and nonexperimental methods of study?

A) Nonexperimental methods involve operational definitions, whereas experimental methods are simple observations.
B) Nonexperimental methods result in definite results, whereas experimental methods simply give a broad perspective of the variables under study.
C) Experimental methods have random variables, whereas nonexperimental methods have manipulated variables.
D) Experimental methods involve the manipulation and control of variables, whereas nonexperimental methods require simple observation of the variables.