We’re all connected. You can send an e-mail message to a friend, and your friend can pass it on to one of his or her friends, and that friend can do the same, continuing the chain. Eventually, your message could reach just about anyone in the world, and it might take only five to seven e-mails for the message to get there.
Scientists recently tested that idea in a study involving 24,000 people. Participants had to try to get a message forwarded to one of 18 randomly(随意地，随机地) chosen people. Each participant started by sending one e-mail to someone they knew. Those who received it could then forward the e-mail once to someone they knew, and so on.
Subjects, who were randomly assigned by researchers from Columbia University in New York, lived in 13 countries. They included an Australian police officer, a Norwegian veterinarian, and a college professor.
Out of 24,000 chains, only 384 reached their goal. The rest petered out, usually because one of the recipients was either too busy to forward the message or thought it was junk mail.
The links that reached their goal made it in an average of 4.05 e-mails. Based on the lengths of the failed chains, the researchers figured out that two strangers could generally make contact in five to seven e-mails.
The most successful chains relied on casual acquaintances rather than close friends. That’s because your close friends know each other while your acquaintances tend to know people you don’t know. The phenomenon, known as the strength of weak ties, explains why people tend to get jobs through people they know casually but aren’t that close to.
So, start networking and instant messaging now. As they say in show business: It’s all about who you know.
If you want to get into touch with a stranger in the world, how many e-mails might it take for the message to reach him/her?

A．5 to 7

B．18

C．13

D．384

Who does the word “subjects” refer to in the passage?

A．the 384 participants who lived in Australuia

B．the Norwegian veterinarians and college porfessors

C．the 24,000 people randomly assigned by reaearchers

D．the 18 people randomly chosen from 13 countries

What does the phrase “peter out” mean in the fourth paragraph？

A．die out

B．pass away

C．disappear

D．pick out

Why do people tend to get jobs more easily through casual acquaintances than close friends?

A．Because close friends don’t talk with each other so much.

B．Because casual acquaintances can help you know more people and make more friends.

C．Because close friends don’t spend so much time gathering together.

D．Because casual acquaintances are kinder and more willing to help others.

In which part of a newspaper will readers read this passage?

A．Culture

B．Entertainment

C．Information and Technology

D．Health