Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A woman is digging under a tree on a tall mountain. She is looking for interesting rocks, and a foot down into the soil, discovers a fossilized fish skeleton. From this discovery, the woman is able to determine that
the mountain used to be underwater
The mountain was once underwater.