Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions from 31 to 36.
Twitter is a social network that allows users to send and receive short messages, called tweets. Tweets can be up to 140 characters long. You can send tweets from your computer or even from your mobile phone. While some social networking services like Facebook or MySpace are more complicated, Twitter is fairly simple to use. To send or receive messages you just have to create an account on Twitter. You can only send texts to Twitter, images are not allowed. Your messages on Twitter can be private, meaning only your friends can read them or you could make them public, meaning they can be seen by everyone. Recently, Twitter has also been used in business. Companies use Twitter to inform people about new products or just to post something that is on sale. Twitter has become very popular. Since its birth in 2006, over one hundred million people around the world have been using it regularly.
