Final answer:
Carbon is central to life because it can form stable covalent bonds with itself and other elements, creating a vast array of complex molecules. It has the unique ability to form four bonds, resulting in structures like long chains and rings, crucial for polymers like proteins and nucleic acids that are fundamental to all life forms. So, the correct option is A.
Step-by-step explanation:
One of the main reasons why carbon is central to life is its ability to form stable covalent bonds with a variety of elements, including itself. This unique characteristic allows carbon to create complex and diverse molecular structures which are essential for life. Carbon has four electrons in its outer shell, enabling it to form up to four covalent bonds. These bonds can result in a multitude of structures, including long chains, branched molecules, and rings, providing a versatile foundation for organic molecules. Furthermore, carbon-based molecules, including carbohydrates, lipids, proteins, and nucleic acids, are imperative for life because they make up cells and facilitate chemical reactions that sustain life processes. Organic molecules built on carbon frameworks are termed polymers, which are made of repeating units called monomers. These intricate carbon-based structures allow for the vast diversity observed in biological macromolecules.
Therefore, among the options provided, the reason that explains why carbon is the central molecule of life is that it can form four bonds, leading to an extensive array of complex organic molecules. These molecules include the carbohydrates, lipids, proteins, and nucleic acids that are the basis of cell structure and function in living organisms.