Final answer:
A molecule is composed of 2 or more atoms and is the correct answer to the provided question. In the biological hierarchy, molecules like DNA play a crucial role in the structure and functioning of living organisms.
Step-by-step explanation:
A molecule is composed of 2 subunits, one nested into the other like a fist in the palm of your hand. In the hierarchy of biological organization, an atom is the smallest and most fundamental unit of matter, which consists of a nucleus surrounded by electrons. Atoms combine together to form a molecule, which is a chemical structure held together by one or more chemical bonds. Many biologically important molecules are macromolecules, such as deoxyribonucleic acid (DNA) and proteins, which consist of monomers linked together to form larger structures. DNA itself contains the instructions for the structure and functioning of all living organisms.