Which of the following best describes a polymer?

A polymer is best described as a large molecule formed by repeating structural units, which are typically called monomers. This structure is significant because it allows polymers to exhibit unique properties and behaviors that differ greatly from those of their individual monomers. For instance, the chemical and physical characteristics of a polymer can change based on the way its monomers are arranged and connected.

Polymers are essential in many aspects of both nature and industry, including plastics, textiles, and even biological materials such as DNA and proteins. Their large size usually makes them much more complex than small molecules, contributing to their varied uses and applications.

Other options do not accurately represent the nature of a polymer. A small molecule is generally referred to as a simple compound, and it does not have the extensive structure of a polymer. A liquid that evaporates quickly describes a property of certain substances that are often volatile, not of polymers themselves. Meanwhile, the term "inorganic compound" encompasses a vast category of substances that do not include the organic frameworks typically seen in polymers. Thus, the description of a polymer as a large molecule with repeating units is the most accurate and relevant definition within this context.