A student has the high dry lens in position and appears to be intently observing specimen The instructor noting a working distance of 1 cm knows seeing How so?

The instructor can tell that the student is using the high dry lens because the working distance is 1 cm. The high dry lens has a shorter working distance than the low power or scanning objective lenses, which means that the objective lens is closer to the slide when it is in use. This allows for a higher magnification of the specimen.