Just a few years ago, biologist and medical personnel were surprised to learn that fetal cells can escape and enter the mother's blood. how can these cells be used in fetal testing?

DNA of these fetal cell can be extracted by identifying fetal cell in a normal blood test report of the mother

Explanation:

In a normal blood test, the screening type is noninvasive which means that no external tools are used for deriving body cell.  

So in such test, the blood is screened to look for the cell of the fetal from which the DNA of the baby can be extracted. This test is predominantly done after the 56 days of pregnancy. The genetic assessment of the fetal DNA is done to determine if he/she has any specific sort of genetic problem such as Down syndrome, etc. After this test is complete, the doctor can recommend for further in depth assessments such as amniocentesis

there really is life in the deepest part

it's c. (to reduce the greenhouse effect/carbon gasses)