This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2019, Subject name: Microbiology
Smallest helminth among the following is: 
Select and explain. 
A. Hymenolepis diminuta, B. Hymenolepis nana, C. Diphyllobothrium latum, D. Balantidium coli
B: Hymenolepis nana
Answer: B: Hymenolepis nana 
Explanation: Smallest helminth among the following is H nana also known as dwarf tapeworm with adult length of 15-44 mm. H. diminuta also known as rat tapeworm has a length of 20-60 cms. Balantidium coli is a large ciliated protozoan (50-130 um) and width 20-70 um) Diphyllobothrium latum can reach upto 30 fts.