This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
An immunocompetent person is infected with Cryptosporidium and developed diarrhea with abdominal cramps. All of the following are TRUE about Cryptosporidium, EXCEPT: 
Select and explain. 
A. Spores are chlorine resistant, B. Acid fast spores, C. Spores are > 100 micro meters, D. Enzyme immune assay is done to diagnose
C: Spores are > 100 micro meters
Answer: C: Spores are > 100 micro meters 
Explanation: Oocysts measuring 4-5 m are passed in feces in enormous numbers and are immediately infectious. Oocysts shed into the intestinal lumen mature to contain four sporozoites; their cell wall provides the unusual propey of acid-fastness, allowing them to be visualized with stains generally employed for mycobacteria. EIA tests are now available for detection of fecal antigen. Prevention of Cryptosporidium infection is limited by oocyst resistance to some of the standard water purification procedures (chlorination) and to common disinfectants. Ref: Brooks G.F., Carroll K.C., Butel J.S., Morse S.A., Mietzneron T.A. (2010). Chapter 46. Medical Parasitology. In G.F. Brooks, K.C. Carroll, J.S. Butel, S.A. Morse, T.A. Mietzneron (Eds), Jawetz, Melnick, & Adelberg's Medical Microbiology, 25e.