Final answer:
Given the context that Giardia lamblia is a pathogen that causes diarrheal disease and the general function of the proteins listed, cwp3 is the most likely candidate to be transported external to the organism, as it is associated with the cyst wall of the parasite.
Step-by-step explanation:
Based on the provided information, Giardia lamblia is known to be a protist that can cause severe diarrhea when ingested and is characterized by its unique appearance using ultraviolet fluorescence microscopy. When analyzing the proteins that this organism might transport externally, the relevant clue comes from the list of potential virulence factors in the passage mentioning proteins like those from type III secretion systems, which are known for transferring effector proteins in some gram-negative pathogens. While the specific proteins listed (cwp3, Histone H4, β-(1-3)-N-acetyl-D-galactosamine, ESV) are not directly mentioned in the given materials, considering the functions of these proteins and the context in which Giardia operates, cwp3, or cyst wall protein 3, is likely to be the protein transported external to the organism itself. Cwp3 is a component of the cyst wall and is related to the parasite’s survival and transmission. It would generally not be expected for Histone H4, which is involved in the structural organization of DNA in the nucleus, or internal cellular metabolism proteins β-(1-3)-N-acetyl-D-galactosamine to be secreted. The abbreviation ‘ESV’ is not clearly defined in the provided information and requires further context.