Which of the following is most commonly responsible for traveler's diarrhea?

Traveler's Diarrhea is defined as three or more unformed stools in 24 hours passed by a traveler, commonly accompanied by abdominal cramps, nausea, and bloating. Its diagnosis does not imply a specific organism, but enterotoxigenic Escherichia coli is the most commonly isolated pathogen. Most cases are self-limited. Rotavirus causes watery diarrhea.