Final answer:
The new position of the submarine is 550 feet below sea level.
Step-by-step explanation:
To determine the new position of the submarine, we need to add the rise in height to its initial position. The submarine is initially situated 800 feet below sea level, and it rises 250 feet. So the new position would be 800 feet minus 250 feet, which is 550 feet below sea level.
Therefore, the correct answer is (c) 550.