The answer is b) animals.
While many organisms can exhibit movement in various forms, not all living organisms have the ability to move actively. Animals, characterized by their ability to move and respond to their environment, do so for purposes such as finding food, escaping predators, and mating. On the other hand, many living organisms, like plants and certain microorganisms, have a fixed position and do not move in the same way animals do. Eukaryotes is a broader category that includes both mobile organisms (like animals) and non-mobile ones (like plants and fungi). Therefore, it is accurate to say that movement is a defining feature primarily of animals.