The correct option is **B. The investigation of matter, its properties, composition, and changes**. ### Detailed Explanation: 1. **Understanding Chemistry**: - Chemistry is often referred to as the "central science" because it connects and overlaps with other scientific disciplines such as biology, physics, environmental science, and materials science. At its core, chemistry focuses on matter, which is anything that has mass and occupies space. 2. **Matter and Its Properties**: - Matter can exist in different states (solid, liquid, gas) and can be classified into pure substances (elements and compounds) and mixtures. Chemistry investigates the properties of these substances, which include physical properties (like color, melting point, and density) and chemical properties (like reactivity and flammability). 3. **Composition of Matter**: - The composition of matter refers to the types and amounts of substances that make up a material. For example, water (H₂O) is composed of two hydrogen atoms and one oxygen atom. Understanding the composition helps chemists predict how substances will behave in different conditions. 4. **Changes in Matter**: - Chemistry also studies the changes that matter undergoes. These changes can be physical (like melting ice) or chemical (like rust forming on iron). Chemical reactions involve the rearrangement of atoms to form new substances, and understanding these reactions is fundamental to chemistry. 5. **Why Other Options Are Incorrect**: - **A. The study of living organisms and their interactions with the environment**: This option describes biology more accurately. While chemistry does play a role in understanding biological processes (biochemistry), the primary focus of chemistry itself is not on living organisms but rather on matter and its properties. - **C. The exploration of celestial bodies and their physical properties**: This option pertains more to astronomy and astrophysics. While chemistry is involved in understanding the composition of celestial bodies (like the chemical makeup of stars), the primary focus of chemistry is not on celestial bodies but on matter in general. - **D. The analysis of economic systems and their impact on the environment**: This option relates to environmental science and economics. While chemistry can contribute to understanding environmental issues (like pollution and resource management), it does not primarily focus on economic systems. ### Summary of Key Points: - Chemistry is the study of matter, its properties, composition, and changes. - It connects with other sciences but has a distinct focus on understanding substances and their interactions. - The other options (A, C, D) pertain to biology, astronomy, and economics, respectively, and do not capture the essence of chemistry. ### Revision Summary: - Chemistry is the central science focused on matter and its properties. - It investigates the composition and changes of substances. - Understanding chemical reactions is crucial for predicting how substances behave. - Other scientific disciplines (biology, astronomy, economics) are related but do not define chemistry's primary focus.