Now, more and more cities are facing problems, such as high housing costs, pollution and crime. Let's see what people in Hyderabad, India and in Sao Paulo, Brazil do to solve   the problems. Hyderabad, India To improve people's lives, Hyderabad is planting more and more trees. The city is even creating _ buildings that use less water and less electricity for power. Adding green to a city has a number of advantages. For example, trees make the air cleaner. In Hyderabad, streets were grey and dirty in the past. However, today they are filled with trees and flowers, making the city cleaner and more colourful. Green areas also give people places to relax or exercise. A study in the USA shows an interesting thing: the greener a neighborhood is, the less crime there is. Sao Paulo, Brazil Many people work in the centre of Sao Paulo, but they don't live there. They've spread out to neighborhoods outside the city because housing is cheaper. Every day, these people travel into the city, and traffic is very heavy. City planners are using different ways to deal with   the problem. First, they are building better subways. Another goal is to make it cheaper for people to live in the downtown area  . Doing this will reduce traffic and pollution in the city. According to the passage, what problem does Sao Paulo have?
A lot of people don't have jobs. Too many people live in the city centre. A lot of people are moving out of the city. Too many people travel into the city every day.