I believe its A because all the other one dont make scene really.
The three chromosomal aberration:
1.) Inversion - breakage of chromosome in two places , the other piece of DNA is re- inserted into the chromosome.
2.) Translocation - the one piece breaks off and attaches to another chromosome.
3.) Deletion - the loss of segment of chromosome.
-ace
<span>Sterilization of animals reduces the level of circulating reproductive hormones leading to increased longevity, typically due to reduce cancer mortality. The primary aim of animal sterilization is avoiding overpopulation, but this increased longevity could be an added benefit for an individual animal.</span>
The more the people, the more pollutant they generate which will pollute the the water.
I'm guessing its so they can be able to diagnose a patient and see whether they need treatment or not