Answer:
C. water freezes (is the answer)
I know I'm super late to answering this because it's a two week old question, but I'll just answer it any way lol.
The main reason why modern chemistry is considered scientific is because to confirm their results, scientists use the scientific method.
What is the difference between the two numbers? That is your answer
Condensation.
If you think about the condensation you may find on your windows on a frosty morning, this may help you to remember :]
Check the picture, I balanced the ions with greater charges first, then I balanced the water last
