9- The results of this type of DNA analysis are often used to help determine *
A) the number of DNA molecules in an organism
B) if two species are closely related
the number of mRNA molecules in DNA
OD) if two organisms contain carbohydrate molecules

B) if two species are closely related.

Explanation:

DNA analysis is used to determine the relationship between two species in order to check their relations with each other because DNA molecules has all the information about the organisms. If there is more similarities between two organisms so they are more closely related to each other while on the other hand, if there is no similarities between two species so we can say that there is no relationship exists between two organisms or species. All this discussion  describes the usefulness of DNA analysis.

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.