What about 1?

[v0031]

Does your class use e-mail? Have you ever tried to write a story for our newspaper and send it in by e-mail? E-mail is used for everything, and it makes life easier. But do you know where e-mail came from?
The man who invented it was Ray Tomlinson, a US engineer. He died early last month at the age of 74.
Back in 1971, Tomlinson was working on something that could send messages from one computer to another. Tomlinson tried to find a way to separate users’ name from the names of their computers. He needed some kind of symbol (符号). However, it couldn’t be a popular one, and it couldn’t be one that computers might know in a different context (语境). It also needed to be on keyboard at the same time. The “@” sign was there, and pretty much no one used it. It was perfect.
“The ‘@’ sign made the most sense,” he told Wired in 2012. “It said where the user was…at.” For example, by writing “Alex at 21st Century Teens” you can send a message to somebody named Alex who works at 21st Century Teens. This was the early form of email.
The interesting thing is that Tomlinson didn’t remember what the very first test message he sent was. “Probably the first message was QWERTYUIOP or something like that,” Yahoo reported, guessing the first row of letters on the keyboard.
Tomlinson, the father of e-mail, changed the way the world communicates and more importantly saved the symbol “@”.
Today, the “@” symbol is finding new life outside of our inboxes (收件箱). Most famously, social media like Weibo and Wechat use it at the beginning of user names. So even if we don’t use e-mail some day, Tomlinson’s contribution (贡献) will certainly live on.

1.Tomlinson chose the symbol @ because
A.nobody used it before   B.it could separate users' names