The answer is B. The reason why is because natural selection causes changes in a populations over many generations, and in this case the change that is being made is the that the population is becoming immune to a disease.
Explanation:
Nucleus Cytoplasm
Contains the genetic material (DNA) Contains a thick gel-like substance
The most obvious structure in the cell Contains all organelles
Contains directions for cell regulation Mostly water
The nucleus is a large and obvious organelle in the cell and it provides instructions for the regulation of the cell's activities and it contains the genetic material (DNA). All organelles are embedded in the cytoplasm which is made up of mostly water.
60 years is three half life for the substance, so 40*1/2^3=5
The age group she does fit in is Infancy