Final answer:
Rocks are not living things because they do not meet the scientific criteria for life, which includes responding to the environment, growth and development, reproduction, maintaining homeostasis, having complex chemistry, and being made up of cells.
Step-by-step explanation:
Rocks are not categorized as living things because they do not possess the characteristics that define living organisms. According to most scientists, for something to be classified as living, it must exhibit seven characteristics: it must respond to the environment, grow and develop, reproduce, maintain homeostasis, have complex chemistry, and consist of one or more cells.
Rocks do not respond to environmental stimuli in the way living organisms do. For example, if you step on a rock, it will not react, whereas a living organism would respond in some way. Also, rocks do not reproduce, they do not grow or develop, they cannot maintain homeostasis, they do not have complex chemistry that allows for metabolic processes, and they certainly do not consist of cells.
While some objects like certain plants might resemble rocks and are colloquially known as "living stones," they are indeed alive because they perform life processes and meet the criteria mentioned above. Similarly, some fossils may contain the remains of once-living organisms, and corals may look like rocks but are actually living animals. These instances can sometimes blur the lines in understanding what is alive and what is not, but using the specific characteristics of life as a guide, we can differentiate that rocks are in fact non-living.