Dna from samples of a virus in 2013 diverged, on average, 9 percent from a virus found in a person from 1983. if the total amount of divergence among contemporary samples is 27 percent, then the virus most likely entered the human population in the year assuming a molecular clock.
a. 1890
b. 1923
c. 1938
d. 1953
e. 1983

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.