There is a reading passage.
SOCIOLOGY

Urbanization describes a population shift from rural communities to large cities. More and more, countries are encountering problems with the rapidly growing rate of big cities. This is even more of a problem in areas where the population boom has surpassed the city’s ability to meet the needs of its people. This has surpassed the city’s ability to meet the needs of its people. This has been case in the Mexican capital, Mexico City. A metropolis of over twenty million people, its resources have become limited. City administrators have been left to deal with problems such as water shortages and heavy traffic. Luckily, city officials are taking news measures to reduce the problems associated with urbanization.
Having a safe and reliable water supply is important to any city in the world. In Mexico City, water shortages have always been a problem. Although the city is situated above an aquifer, it is not enough to supply the overwhelming number of inhabitants with the water it needs. In order to counter the water shortage, city officials have begun to explore options for obtaining water from other sources, namely states that surround the federal district. Additionally, they have launched a city-wide campaign to raise awareness about water conservation among the city’s citizens.
The dense population of Mexico City inevitably creates traffic jams that can last for hours. In order for the city to properly function, its inhabitants need to have a way to get around quickly and easily. Mexico City’s response to the traffic problem was to form a partnership with an organization. Their partnership will help city administrators improve public transportation. Among the changes is the replacement of old, unreliable buses used for public transportation. This will increase efficiency by avoiding mechanical failures. Moreover, extra routes will be added in order to serve a greater part of the population. The improvement in public transportation is expected to ease traffic congestion by reducing the number of cars on the road.
The word it in the passage refers to
(A) Mexico City
(B) population
(C) aquifer
(D) water shortage
The answer is (C).
I chose (A) because I thought that the words “it” in this sentence are same.
Although the city is situated above an aquifer, it is not enough to supply the overwhelming number of inhabitants with the water it needs
Could you help me?