If you see a group of people dancing and singing on the street or in the railway station,  you don't need to feel surprised．They are a flash mob （快闪族）, which is a group of people who come together suddenly in a public place, do something unusual for a brief period of time,  and then quickly break up．They are usually organized with the help of the Internet or other digital communication network．At a predetermined time, they gather and perform some  distractions（消遣） such as waving their hands and exchanging books, Then, they quickly break up before the police can arrive．Using mobile phones, the flash mob can change its location if the first one has been replaced for any reason．
Bill Lasik, senior editor of Harper’s Magazine, organized the first flash mob in Manhattan in May 2003 and the first successful flash mob came together on June 3, 2003 - after the first attempt was foiled at Macy's department store．Lasik claimed that the activity was designed to make fun of hipsters （起时髦的人）, and call attention to the cultural atmosphere．       
Flash mob gatherings can sometimes shock people．Such an activity might seem amusing and untrue, but it also might frighten people who are not aware of what is taking place．Undoubtedly, flash mobs can serve as good political tools in any direction．They also have great economic potential, such as using flash mobs to advertise a product．
The flash mob is now becoming more and more popular．People use it to do many things．For example, in 2009, Michael Jackson's fans took part in a flash mob to remember him．Hundreds of his fans gathered singing and dancing Michael's famous song "Beat It" together．Flash mobs give people from all walks of life an opportunity to come together to create a memory．
The undefined word "foiled" in Paragraph 2 can be replaced by _     。

A．forgotten

B．prevented

C．announced

D．confirmed

What can you learn about the flash mob from the passage?

A．The flash mob usually breaks up quickly for lacking enough time．

B．Once the place for the activity is determined, it can't be changed．

C．The flash mob can be made use offing many fields just for fun．

D．It gives people the chance to come together to do something unusual．

The main purpose of the passage is -

A．to entertain	B．to encourage
C．to inform	D．to persuade

The writer's attitude towards the flash mob is

A．negative

B．favorable

C．objective

D．doubtful