The correct option is D.
The Mexico city was built on the ruins of an old lake. The lake was drained in order to provide the needed land for the city and water has to be regularly pump out of the underground aquifers in order to prevent flooding and also to provide drinking water for the city. This affected the supporting soil structure and result in the sinking of the city. The city has sunk by about 30 feet in the last 100 years and this has caused a lot of damages which are quite expensive to repair.
The story is told in strict first-person narration
