题目内容：

    Large gatherings such as weddings and meetings can be socially flooded with people. Learning people's names only adds to the stress. A new facial-recognition app could come to the rescue, but experts suggest people should be careful while using it.

The app, called SocialRecall, connects names with faces through smartphone cameras and facial recognition (识别), avoiding the need for formal introductions. "It breaks down these social barriers we all have when meeting somebody," says Barry Sandrew, who created the app and tested it at an event attended by about 1,000 people.

After receiving an invitation to download SocialRecall from an event organizer, the user is asked to take two selfies and sign in through social media. At the event, the app is active within a previously set geographical area. When a user points his or her phone camera at an attendee's face, the app identifies (识别) the person, displays the person's name, and links to his or her social media information. To protect Privacy (隐私), it recognizes only those who have agreed to use. And the app's creators say it automatically removes users' data after an event.

Ann Cavoukian, an expert who runs the Privacy by Design Center of Excellence praises the app's creators for these protective measures. She added, however, that when people choose to share their personal information with the app, they should know that "there may be unexpected results down the road with that information being used in another situation that might come back to bite you."

The start-up project has developed the app for people who suffer from prosopagnosia, or "face blindness," a condition that prevents people from recognizing people they have met. To use this app, a person first receives an image of someone's face, from either the smartphone's camera or a photograph, and then tags it with a name. When the camera spots or recognizes that same face in real life, the previously entered information is displayed. The collected data are stored only on a user's phone, according to the team behind the app.

1.Social Recall is used to                .

A.take photos B.identify people

C.organize events D.make friends

2.Paragraph 3 is mainly about              .

A.how the app works

B.how the app was created

C.what makes the app popular

D.what people can do with the app

3.SocialRecall helps people with prosopagnosia by            .

A.giving names to the photos kept in their smartphones

B.collecting information previously entered in the phone

C.providing the information of a person when they first meet

D.showing the person's information when it spots a stored face

4.What can we learn about SocialRecall from the passage?

A.It may put people's personal information at risk.

B.It has caused many unexpected results.

C.It can stop people recognizing people they have met.

D.It is praised by users for its protective measures.