Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

        Urbanization programs are being carried out in many parts of the world, especially in densely (23) ________ regions with limited land and resources. It is the natural outcome of economic development and industrialization. It has brought a lot of benefits to our society. However, it also (24) ________ various problems for local authorities and town planners in the process of maintaining sustainable urbanization, especially in developing countries.

When too many people cram into a small area, urban infrastructure can't be effective.                 There will be a (25) ________ of livable housing, energy and water supply. This will create overcrowded urban districts with no proper facilities. Currently, fast urbanization is taking place predominantly in developing countries where sustainable urbanization has little relevance to people's lives. Their houses are just shabby slums with poor sanitation. Their children only manage to get basic education. Hence, the struggle for (26) ________ is their first priority rather than anything else. Only when the quality of their existence is improved, can they seek (27) ________ other high values in their life.