Answer:
Option B.
Explanation:
The surface of a river has been marked as (-225) feet and the top of the building at (+18) feet.
If we consider surface sea as a base line to calculate the altitudes of certain place, then altitudes above the the river surface will be positive and the altitudes below the river surface will be negative.
Therefore, (-225) feet of a river means 225 feet below the sea level.
+18 feet of a building means 18 feet above the sea level.
Option B, is the answer.