I believe that your option C would be the correct answer. We know that water can turn to a solid materail because during cold temperatures, water turns to ice.
We know that water can turn to gas, as water can evaporate.
And also, we know that water is obviosly a liquid.
Therefore, Option C would be your answer.
I think the answer will be Graphite.
Answer:
Since different isotopes of an element have different numbers of neutrons (but always the same number of protons) they have different mass numbers. Nitrogen-14 and nitrogen-15 are both stable isotopes of nitrogen. However, the other 5 isotopes are all unstable.
