An example of "soft" energy mentioned in this passage is ______.

单项选择题According to the passage, highway building______.

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)______.