单项选择题According to the passage, which is the real reason for people to move from rural to urban areas
单项选择题In 1991, New York was the world's ______urban are
单项选择题Which of the following organizations is partly responsible for the increase of gun-related crimes______
单项选择题Hijacking of cargo is a(n)______.
单项选择题According to the passage, prostitution falls into the category of______.