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

     People enjoy living in large cities. But cities have problems. One problem is that they frequently grow very rapidly. Transportation (23) _______ complicated. There are a lot of cars, buses and bicycles. As a result, people are trying to improve the big cities, and they are also planning for new cities. Plan A is a large city (24) _______ smaller cities around it. There is an open land with trees, fields, and lakes between the large city and smaller cities. Each small city is (25) _______. It has offices, schools, hospitals, and places of entertainment. In Plan B the cities are (26) _______by a road. In Plan c, the cities are in rings around the central city and all of them are connected to each other. The goal of all these plans is to limit the (27) _______of the large city.

Transportation (23) _______ complicated.