A Level Biology Practice Exam 2025 – All-in-One Study Guide to Excel in Your A Levels!

The correct answer is DNA because it is a complex molecule made up of repeating units called nucleotides. Each nucleotide consists of a phosphate group, a sugar, and a nitrogenous base, and when these nucleotides are linked together through covalent bonds, they form a long chain that constitutes the DNA polymer. This structure allows DNA to perform its key role in storing and transmitting genetic information.

In contrast, glucose is a simple monosaccharide, and while it can polymerize to form polysaccharides like starch and glycogen, glucose itself is not a polymer. Fatty acids are building blocks of lipids and do not form long chain structures in the way polymers do; instead, they can join together in different ways to form triglycerides or phospholipids but do not create long repeating chains characteristic of polymers. Amino acids are the building blocks of proteins and can link together to form polypeptides, which are indeed polymers, but the option refers specifically to DNA as a polymer in this context.