This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: parasitology, Subject name: Microbiology
Which of the following is true about giardia - 
Select and explain. 
A. CFT is diagnostic, B. Trophozoites and cysts are seen in man, C. Lives in lower intestine, D. Invades normal mucosa
B: Trophozoites and cysts are seen in man
Answer: B: Trophozoites and cysts are seen in man 
Explanation: Life cycle The trophozoites of the parasite multiply in the intestine of man by binary fission.During unorable conditions in the duodenum,encystment occurs,usually in the colon.Infection of man occurs by ingestion of cysts in contaminated food and water.Infective dose is 10 to 100 cysts.Within 30 minutes of ingestion the cyst hatches out two trophozoites which then multiply and colonise in the duodenum.Due to high acidity of duodenum,Giardia often localize in the biliary tract (refer pgno:31 baveja 3 rd edition)