The answer is C.
Because if it is not Medical Science then C is the answer you are looking for
detoxification is the answer.
I would say, A. Endoscopy because, it is a tube that goes down the throat or the other way and looks through the digestive tract and the throat cavity.
The human body is mostly made up of water (H2O), and there is one oxygen atom in each molecule of water. Note that, although each water molecule also contains two hydrogen atoms, the atomic mass of hydrogen (about 1) is much smaller than the atomic mass of oxygen (about 16). Because of this, hydrogen contributes less to human body mass than oxygen.
