Which one of the following is true about Giardia?

The flagellate protozoan Giardia intestinalis (previously known as G lamblia), its causative agent, is the most common protozoal intestinal parasite isolated worldwide. Ingestion of as few as 10 Giardia cysts may be sufficient to cause infection. The trophozoite also contains 4 pairs of flagella, directed posteriorly, that aid the parasite in moving. It inhabits duodenum and upper jejunam.