Wilma and stanley are expecting their first child, and a prenatal test indicates that the child has a chromosomal abnormality. they spend several weeks educating themselves about the condition and preparing for how their child may be limited, but when the baby is born, there is no problem and chromosomal mapping reveals no abnormality. what happened?

The cells analyzed might be a mosaic of different genomes

Explanation:

The human genome in every cell might not be the same and could give us some misrepresentation of what really happens on our genome. Chromosomal abnormalities are also a very common phenomena to be observed in human cells. For those differences in the genome of the child the test might have identified some altered cells with a type of chromosomal abnormality which was not latter identified or the abnormal cell might be also eliminated by its abnormal nature.

i believe it would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.