Answer:
A. end up at exactly 0 feet of elevation.
Explanation:
This is because, at a depth of 20 feet, their position is -20 feet below the water surface. If they rise by 20 feet, we add 20 feet to their current position to reach their new position.
So, -20 feet + 20 feet = 0 feet.
So, their new elevation will end up at exactly 0 feet of elevation.