Different amount of species in an area.
Answer: increasing number of protons increases the positive charge of the nucleus.
Explanation: because as the electronegativity moves from left to right on the periodic table the protons do increase to make it into a positive charge.
The formula for water is H2O so there would have to be two Hyrdogens and one oxygen. Therefore it would be 4g of Hydrogen and 16g of Oxygen leaving you with 20g.
The answer is D.
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D. 6 protons and 7 neutrons
As proton remains constant
A, B and D should be the ones you should check