Answer:
Water
Explanation:
A compound means a substance (something) that is made of 2 or more elements.
Elements are the substances found on the periodic table. If you can find something on the periodic table, it cannot be a compound.
Nitrogen is "N" (7th square).
Phosphorus is "P" (15th square).
Oxygen is "O" (8th square).
The compound "water" is H₂O. It uses the elements "H" (hydrogen) and "O" (oxygen).
Since water is the only compound in those choices, the answer has to be water.
Other facts!
The Earth's surface has mostly water. About two-thirds (2/3) of Earth's surface is water.
The Earth's atmosphere is mostly Nitrogen (78%).
We breathe oxygen (which is O₂).
