Directions: Read the following passage carefully. The passage is followed by some questions or unfinished sentences. For each of them there are four choices marked A, B, C, and D. Choose the best answer to each question.Questions 11 to 15 are based on the same passage. Grammar is an aspect of language about which learners have different opinions. Some learners are very interested in finding out or learning grammar rules and doing lots of grammar exercises. Others hate grammar and think it is the most boring part of learning a new language. Whatever opinion you have, however, you cannot escape from grammar; it is in every sentence you read or write, speak or hear. Grammar is simply the word for the rules that people follow when they use a language. We need those rules in the same way as we need the rules in a game. If there are no rules, or if everybody follows their own rules, the game would soon break down. It's the same with language; without rules we would not be able to communicate with other people. So you cannot escape from grammar, but the key question here is: What is the best way to learn grammar? You can learn the rules of a game by simply playing the game. You will certainly make mistakes; you may even get hurt. Eventually, however, you will know how to play. Of course, the rules of a language are very much more complicated than the rules of any game, but in fact this is exactly how you learned your own language. Nobody taught you the rules of your mother tongue as you were growing up but now you never make a grammar mistake. Most people learning a new language do not have so much time and such an ideal situation. So, there is no easy answer to the question. There are just as many different opinions about teaching grammar as there are about learning grammar. Many teachers believe in the importance of grammar lessons devoted to a study of language rules and lots of practice exercises. Other teachers feel that grammar is best learned by doing different language activities without focusing so directly on the rules. Whatever your opinion about grammar and whichever is the way you are taught, you need to use different strategies to help you learn grammar more effectively.Question 11 is based on the above passage.How is grammar defined in the passage?