Which of the following is true of cholera-
Vibrio causes secretory diarrhea.

About Other options:

Recent epidemics are due to O1 ElTor and also O139 serovar. (Classical still exists and few cases were reported from Bangladesh)
Vibriocidal antibodies in serum (titer 1:20) have been associated with protection against colonization and disease. …………… Jawetz 25/e p237
Endotoxin (LPS) does not play any role in pathogenicity of cholera but is responsible for immunity developed by killed vaccine.
Recent epidemic was due to classical type
Causes secretory diarrhoea
Caused by endotoxin
Vibriocidal antibodies correspond to susceptibility