What evidence supports the hypothesis that rats and fleas were the main cause of the spread of the bubonic plague? What evidence refuted this hypothesis?

The answer is below

Explanation:

The evidence that support that the rat and fleas were the main cause of the bubonic plague is the discovery of efficient transmission of Yersinia pestis, that is considered to occur as a result of the bites of fleas, particularly, flea-bearing rodent whose mid guts become obstructed by replicating Y. pestis a few days after it has fed on an infected host.

Hence, the blockage leads to starvation and intensive mode of feeding attitude by fleas, and in attempt to constantly clear their blockage by regurgitation, this leads to thousands of plague bacteria being flushed into the feeding site, thereby infecting the host.

However, The evidence that refuted the hypothesis that the rat and fleas were the main cause of the bubonic plague, is the observation of epizootic modelling plague in prairie dogs, this suggested that occasional reservoirs of infection such as an infectious carcass, rather than "blocked fleas" are an elaborate and more detailed explanation for the observed epizootic behaviour of the disease in nature.

what are the choices?

health care plans in the united states having high costs because they are focusing on providing quality programs for different groups of individuals. the quality of the service is based on money flow received from the members. without this investment, couldn't be possible a constant scientific searching to prevent death and illness caused because of low levels of health investigation. currently, the complaints are not about the highest cost, but about the coverage and benefits to access the necessary health services required by the members.  

besides, if a global health system is established the quality levels will fall down because of the standardized of the health. the access to care will increase but the quality will be low because it depends on the money invested.