What defines a nanomaterial?

A nanomaterial is specifically defined by its properties and size at the nanoscale, typically being between 1 and 100 nanometers in size. This size scale brings about unique physical, chemical, and biological properties different from those of bulk materials. Therefore, the presence of nanoparticles or the reliance on nanotechnology characterizes a material as a nanomaterial. In this context, option B accurately captures the essence of what defines a nanomaterial, as it includes both the presence of nanoparticles and the application of nanotechnology, which is foundational to the field. This focus on size and the unique properties associated with nanoscale materials is what sets nanomaterials apart from others.

The other options fail to correctly define nanomaterials because they either refer to larger sizes than what is considered nanoscale, narrow down the materials to specific types, or fail to consider the size aspect altogether, which is crucial in the definition.