阅读下列短文, 从给的四个选项 (A、B、C和D) 中, 选出最佳选项。
体裁：说明文 话题：网络时代 时间：6分钟
Think about how many ways there are for you to communicate today.You can send a letter or pick up the phone and make a call.But today，one of the most popular ways to communicate is called instant messaging(IM)．In any instant messaging system，you type a little text message on your computer，press the “Send” button，and your message instantly shows up on your friend's screen.But how does it work?
Actually，the whole process is very cool.In the 1980s，you could sit down at a computer at any big university.Up to 100 people would be logged in and share the computer because these computers were very expensive.You could type a command to send an instant message to anyone logged in the same computer.It felt like everyone was connected together no matter where they were sitting.
Today，you can communicate with anyone in the world.All you need is an instant messaging program installed on your computer.There are many programs to choose from.AOL's instant messenger is probably the most popular right now.MSN has one.Google has Google Talk.
