Correct Answer: A
Explanation:
Perhaps the most compelling reason it is difficult to define life is the lack of objective measuring tools. All of our human methods for defining the undefinable (science, philosophy, religion, metaphysics, etc.) are self-limiting in some way. Unlike other living organisms, human beings seem to be driven to quantify and categorize the world around them. If we can describe a phenomenon such as "life" well enough, we can bring some order out of chaos. The problem is, once one working definition has been created, a previously unknown plant or animal may appear and defy the definition.