What does chemistry primarily study?

Chemistry primarily studies the composition of matter and the changes that matter undergoes. This encompasses understanding the various substances that make up the world around us, including their properties, structures, and how they interact with each other. In chemistry, the focus is on how matter is formed, what it is made of, and how it transforms during chemical reactions. This foundational aspect of chemistry provides insights into everything from simple substances to complex biochemical processes, which can be essential in various scientific fields, including medicine, biology, and environmental science.

Although the other options touch upon important aspects of chemistry, they do not encompass the breadth of its study as comprehensively as the correct answer does. The reactions of living organisms, for instance, fall under the specific area of biochemistry, which is a sub-discipline of chemistry. The study of chemical formulas is more about the representation of chemical substances rather than the holistic view of matter and its changes. The interaction between different chemicals is indeed a part of chemistry but is limited to specific reactions instead of addressing the overall composition and transformation of matter. Thus, the correct answer captures the essence of what chemistry entails.