The negative stain is used to the negative stain is used to determine cell size. visualize endospores. determine flagella arrangement. visualize the outer membrane. determine gram reaction.

The correct answer is to determine the cell size. The negative stain is particularly useful for determining cell size and arrangement. It can also be used to stain cells that are too delicate to be heat-fixed. This procedure uses Nigrosin, which is a acidic strain.