What type of disease causing organism is so small you must use a microscope to see it? a) carryon b) pathogen c) protozoa d) vices

Bacteria are the smallest micro-organisms, ranging from between 0.0001 and 0.001 mm in size. Phytoplankton and protozoa range from about 0.001 mm to about 0.25 mm. The largest phytoplankton and protozoa can be seen with the naked eye, but most can only been seen under a microscope.

Therefore your answer would be (C)

I belive this would be C. protozoa.