Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word for each of the questions from 44 to 50. 

     Many people see large urban cities as a wonder of human imagination and creativity. They represent how far the human population has come in terms of community development. Despite its positive things, there are also negatives from urbanization on the physical health of humans living. 

     As it would be expected, developing countries tend to see more negative physical health effects than modern countries in regard to urbanization. One example of a developing country experiencing these problems is China. China is a country that in the past 30-40 years went from being an agrarian based society to a significant industrialized country. This industrialization has in effect caused the need for more centralized cities, centralized meaning having lots of jobs and living spaces within a close proximity. In most recent decades, since China's change to being more of an industrial based economy, the country has experienced record high numbers of people migrating within its borders. In effect, the number of cities with over 500,000 people has more than doubled. These migrations are typically of people from rural areas of China moving to the new urban areas. Due to this large influx in the urban population, there are many possibilities for health challenges among these people. 

     One very common and fairly obvious negative aspect of highly congested urban areas is air pollution. It could include particulate matter, most commonly attributed to industrial plants and refineries waste, or chemicals like CO2 or Methane. Due to a vast number of people in these urbanized cities, the air pollution is known to be very extreme. These conditions can lead to many different health problems such as: Asthma, cardiovascular problems or disease. When exposed to these conditions for a prolonged period of time, one can experience even more detrimental health effects like: the acceleration of aging, loss of lung capacity and health, being more susceptible to respiratory diseases, and a shortened life span. 

          Another way that urbanization affects the populations' health is people's change in diet. For instance, urban cities tend to have lots of accessible, quick, and easy to get food. This food is also more than likely not as high quality as well as contains a large amount of sodium and sugar. Because this food is so accessible, people tend to eat it more. This increase in consumption of low-quality food can then lead to diabetes, hypertension, heart disease, obesity, or many other health conditions

The word “it” in the last paragraph refers to _______.