Is the water of hydration covalently bound to the compound?

You encounter a solution that is acidic and you decide to test it by adding a small amount of a strong acid. the ph lowers slightly but is approximately unchanged, and still remains acidic. what can you say about the solution? a. it is a buffer solution. b. it is not a buffer solution it is a strong acid solution. d. the solution has been neutralized. e. the solution has excess acid present

Why does a plastic bottle that is sealed at a high altitude change it’s shape when taken to lower altitude

Ab c or d ? i’m not sure what the answer is