Shenzhen's fast development has made it become China's most crowded city! There are about 15 million people living on its 1991square kilometers. On each square kilometer averagely live 7500 people. It is 1080 more than that in Hong Kong, and nearly 800 more than that in Guangzhou. Besides, Shenzhen owns 2 million local vehicles, and about 300000 vehicles from other places also run on the local roads every day. The total length of the city's road is 6041 kilometers. It means each resident only owns 0.58 meters of road! As a result, the city is facing serious environmental and resource problems. One of the problems is water shortage. The amount of fresh water for each person of the city is only 25% of the country's average. What's more, most of the water drunk by Shenzhen people comes from other areas. There are   _   people living in Shenzhen now.
about 1991 about 15000000 about 150000 about 300000