单项选择题

Today, learning English involves much more than studying a text book and doing tests. Let"s look at a couple of the most popular social networking opportunities available to you.
Twitter
Twitter is a social networking site that demands precision of expression where each post or "Tweet" you can make is limited to 140 characters. Therefore, you"re forced to choose your words carefully and to convey your message clearly. This is excellent for improving your English as you eliminate unnecessary words.
Facebook
Facebook is a social networking service whereby users can create a personal profile, add other users as friends, and exchange messages. You can post text, pictures, images, video, and music on your Facebook page. You gain English writing experience through composing your various messages. Facebook exposes you to a significant selection of writing (text) in which to build your English skills.
Skype
Skype is a computer software application that allows users to make calls over the Internet. Calls to other users of the skype service are free. Skype allows you to talk, and/or text and add videos. As concerns improving your English skills, skype gets you talking. Consequently, you converse, which is putting your English speaking and listening skills into action. There are even teachers on skype who offer traditional English lessons and there are conversational groups that meet more informally.
LinkedIn (领英)
If facebook and Twitter sound a bit frivolous (无聊的) for your tastes, you might prefer LinkedIn which is a social networking site for professionals. It"s an excellent site for connecting with other professionals, be it in business or other organizations.
YouTube
YouTube is a video-sharing website. Users upload, share and view videos on this social networking site. Learning English via YouTube involves listening to the language via the videos you view. You also learn through reading the comments posted in English, situated below each video.
Flickr (网络相簿)
Flickr is a social networking site with a difference, because you build contact with people by sharing photographs, and short videos. If you have a digital camera, you can share your life with an online community. There are groups for countries, hobbies, animals, just about anything you can think of.
When you choose somewhere to network, keep some control over the information you display. The passage maybe mainly for （）.

点击查看答案&解析