Magnifying glasses also enlarge the image of objects, then why do you think was the discovery of microscope essential?

Magnifying glasses only enlarges the image of specimen that are visible to the naked eye, however, resolution is lost and some details are not shown in the magnified image.

This gap gave rise to further research on increasing the image size and further details without losing the resolution. Also certain micro organisms and viruses can not be seen unless with the aid of a very high series of power lenses.

This gap made the discovery of microscope essential.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.