In the 1800 many people living in cities in the US died of infectious diseases such as Cholera which is caused by a bacterium found in the feces of a infected person that pollutes water due to lack of water sanitation. Cholera is no longer a major problem in the US but is still a problem in many countries around the world .What is the most likely reason for the elimination of cholera as a major disease in the US A) sewage treatment plants have eliminated such pathogens from drinking water
B) ppl have learned the importance of washing their hands
C) Advances in medicine have led to cures for cholera
D) Regulations have prevented factories from dumping pollution into lakes and rivers

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

What are the three types of counseling established by marine corps policy?

What are the two functions of the respiratory system