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.
When you are awake all the time
The largest river in the world is the Amazon River, 4,345 miles in length located in South America.
