Which field of science studies the nature of matter and its changes?

The correct choice, chemistry, is the field of science that focuses specifically on the study of matter, its properties, the changes it undergoes, and the reactions it can participate in. Chemistry examines the composition, structure, and behavior of substances at a molecular and atomic level. This includes exploring how different substances interact with each other, how they can transform into different substances during chemical reactions, and the energy changes that accompany these processes.

In comparison, physics primarily deals with the fundamental principles of forces, energy, and motion, rather than the chemical composition of matter. Biology concentrates on living organisms, their development, functions, and interactions with the environment, excluding a detailed examination of the properties of non-living matter. Geology focuses on the Earth, including its physical structure and substance, the processes that shape it, and the history of its formations, which are not primarily concerned with matter at a molecular level like chemistry is.