Which term refers to substances that relate to living organisms?

The term "organic" refers to substances that are derived from living organisms or are related to the chemistry of carbon-containing compounds, which are fundamental to life. Organic compounds typically include a wide variety of substances such as proteins, lipids, carbohydrates, and nucleic acids, all of which play critical roles in biological processes. The defining feature of organic materials is their carbon backbone, which allows for the complex structures necessary for life.

In contrast, nanoscale, nanomaterial, and nanocomposite pertain to dimensions and the characteristics of materials at the nano-level, which is relevant in fields such as nanotechnology but does not inherently relate to living organisms. Nanoscale indicates sizes on the order of 1 to 100 nanometers, nanomaterials are structured in this scale, and nanocomposites combine materials at the nanoscale but do not inherently involve biological substances. Thus, the correct choice highlights the connection of the term "organic" to the essence of life and living organisms.