Choose the word or phrase - A, B, C or D - that best fits the blank space in the following passage.
Mexico City is growing quickly. In 1970, the city had about 9 million people. Now it has over 17 million. All these people are causing ___(1)___ _____ for the city. There are not ___(2)___ _____ jobs.
Also, there is not enough housing. Large families have to live together in small homes. Many homes do not have water. They also do not have bathrooms or electricity. The Mexican government is ___(3)___ _____ about all these problems. It is working hard to make ___(4)___ _____ better in the city.
Why is Mexico City growing so ___(5)___ _____? Where are all these people coming from? They are coming to the city from the country. Life is hard on the farms in Mexico. Most people on farms have to live a very simple life. They have no ___(6)___ _____ money for modern things. People think life in the city must be ___(7)___ _____ . So they leave their farms and move to Mexico City.
All around the world, large cities have the same problems. One of them is air ___(8)___ _____ Mexico City has bad air. It is dirty and ___(9)___ _____. Cars are one reason for the dirty air. Many Mexicans now own their own cars and drive in the city. The factories in the area also cause air pollution. These factories put a lot of ___(10)___ _____ into the air. It is not easy to clean up the air in a large city. The government has to make new laws, and everyone has to help.