In the park，you see a group of people，all looking up at the sky． Without thinking about it， you look upwards， too． Why？ In the concert，someone begins to clap and suddenly the whole room joins in． You do， too． Why？

    Sometimes we feel we are acting correctly when we do the same as others． The more people follow an idea， the better or truer we think the idea is． It's the social proof （社会认同感）that works．

    The scientist Asch carried out an experiment． It shows how social proof can influence us． In a room， a man is shown Line 1，and next to it are three lines （A，B，C）． A is longer，C is shorter and B is as long as Line 1． He must tell which of the three lines is as long as Line 1． When the man is alone，he gives the correct answer B． Then， five other men enter the room， and each of them gives the answer C as they were told to． Now the man changes his idea and gives the answer C． Asch got the same result many times among different subjects （实验对象）．

    Why do we act like this？Well，in the past， following others was a way to keep from danger．Suppose that 5000 years ago you were hunting （打猎） with friends．Suddenly，they all ran away．What would you have done？ Would you have stayed？ No，you would have run，too．We are descendants （后代） of those who copied others' action． It is so deeply planted in our mind that we still use it now．

    Social proof has special power．The advertising industry，for example，often makes use of it．So be careful whenever a company says its product is "the most popular"．

（1）At the beginning of the passage， the writer leads in the topic by 　　．

A．telling a story

B．giving examples

C．answering questions

D．showing a map

（2）According to Paragraph 3， the experiment by Asch shows 　　．

A．following others is always right

B．social proof may change people's ideas

C．it's difficult to carry out the experiment

D．people can study better if they are alone

（3）The underlined word "It" in Paragraph 4 refers to 　　．

A．running with others

B．hunting with friends

C．copying others' action

D．doing something different

（4）According to the passage，we can infer （推断）that 　　．

A．it's important to run with others anytime

B．products in the advertisement are the best

C．we mustn't copy others' action to keep safe

D．we need to think twice before following others