True about Cholera -a) Food can transmit cholerab) Vaccination gives 90% efficiencyc) Healthy carrier can transmit cholerad) Chlorination is not effective: (A) ac, (B) bc, (C) ad, (D) b
Answer is A. Cholera is transmitted by contaminated water & food, direct contact through finger from carriers
About Other Options:

Option b: Vaccination gives protection rate of 50–60% ………………. Ananthanarayan 9/e p311
Option d: Chlorination is effective. ‘In rural area, water can be made safe from cholera bacilli by boiling or chlorination’