Answer: Option A
Explanation:
It is not that the doctors are not competent ,they were sent by the government, the government can't send incompetent doctors to solve an epidemic ,but it is going to be ommited variables by the doctors on the sickness, yes it takes time to figure out the root of sickness, looking at the period of early 19th century, medical method might not have reached a convincing level ,so there is possibility of omitted variables, maybe there were not able to have much time to figure out the sickness that might caused the death. So option A is the best possible answer.