be about tobe sure 的用法
1. be sure of/about sth/doing sth，意为“确信......”；“对......有把握”。但在接名词时，be sure of 侧重指主语对某抽象事物的确信无疑；而 be sure about 则侧重指主语对某具体事物的确信无疑。
例如：He is sure of success. 他自信会成功的。
      I'm sure of his honesty. 我肯定他是诚实的。
      However, he went on to explain that he was not sure about two things ---- the grammar and some of the idioms. 不过，他接着就解释说，他在语法和某些习惯用语方面都没多大把握。
      If you are not sure about the situation in the world, you can read the newspaper every day. 如果你对世界形势不大了解，你可以每天看看报纸。
 
    若后面要接反身代词，则只能用 be sure of, 即 be sure of oneself,意为“有自信心”。
例如：Joan will sit for an important examination next week, but she is not sure of herself. 琼下周要参加一个重要考试，但她对自己没有十分把握。
 
2. be sure to do sth，表示说话人对句子主语作出的判断，认为句子主语“必定”、“必然会”、“准会”......。
例如： It is sure to rain. 天一定会下雨。
      He is sure to have known about that. 他准会知道那件事。
      He told me I was sure to get a warm welcome. 他告诉我，说我准会受到热情接待的。
 
    然而be sure to do 用在祈使句中，不是表示判断，而是表示对对方的要求，意为“务必要”，“一定要”。
例如： Be sure not to forget it! 千万别忘记呀！
      Be sure to send my regards to your mother. 务必代我问候你母亲。
      Be sure not to do that again. 一定不要再干那种事了。
 
3. be sure + 宾语从句，表示主句主语对宾语从句中涉及的事物所作出的判断，意为“确信某事一定会......”。
例如： I'm not sure whether I've met him before. 我不能确定以前是否见到过他。
      We are sure he will make great progress this term. 我们确信他这学期一定会取得巨大进步。

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