国有其君，家有其主，文章也要有其主。一个主题句放在文章的开头(保险型)或者结尾，让读者一目了然，也会让你在写作文时有个参考，不跑题。

　　特别提示：隐藏主体句可是要冒险的!

　　To begin with, you must work hard at your lessons and be fully prepared before the exam(主题句). Without sufficient preparation, you can hardly expect to answer all the questions correctly。