The discovery of the instrument with lenses for making very small objects appear larger widened our scope of knowledge.

Answer: Option C

One word substitute is Microscope.

Telescope: an optical instrument designed to make distant objects appear nearer, containing an arrangement of lenses, or of curved mirrors and lenses, by which rays of light are collected and focused and the resulting image magnified.
Binoculars: an optical instrument with a lens for each eye, used for viewing distant objects.
Microscope: an optical instrument used for viewing very small objects, such as mineral samples or animal or plant cells, typically magnified several hundred times.
Bioscope: a cinema or film.