At first, atoms were considered to be very simple and indivisible. People form ancient times knew only of water, earth, fire, and air, not what constitutes them or how they work specifically. Now, there are 118 elements and all atoms are proven to consist of neutrons, protons, and electrons, and that's just the beginning of it.
Answer:
Explanation:
Our 
sample yielded 1g of 
and 16g of 
, but our unknown sample yielded 2 times as much for the same amount of .
What does this mean? that the H:O proportion for the unknown sample is twice the H:O proportion for the sample.
What is the H:O proportion for the sample? As we can see from its formula, it's 1:1, therefore the proportion for the unknown formula must be 2:1.
That means, two H atoms for every O atom. We could write that as: 
and you should recognize that formula, for it is one of the most common compounds on earth, Water.
D is the answer - plate boundaries
