Which of the following is an example of a macromolecule?

Macromolecules are large, complex molecules that are typically formed by the polymerization of smaller subunits. They include proteins, nucleic acids, carbohydrates, and lipids, which are essential for various biological functions. DNA, in particular, is a type of nucleic acid that carries genetic information and is composed of long chains of nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base, and they are linked together in a chain to form the structure of DNA. This extensive arrangement of nucleotides makes DNA a quintessential example of a macromolecule.

In contrast, amino acids and glucose are smaller molecules. Amino acids serve as the building blocks for proteins and are relatively small compared to macromolecules. Glucose, a simple sugar, is a monosaccharide and serves as an energy source but does not qualify as a macromolecule. Water is a simple molecule composed of hydrogen and oxygen and does not fit the definition of a macromolecule either. Therefore, DNA stands out as the clear answer due to its size and complexity as a macromolecule.