1. besure of/about sth/doingsth，意為“確信......”；“對......有把握”。但在接名詞時，be sure of 側(cè)重指主語對某抽象事物的確信無疑；而be sure about 則側(cè)重指主語對某具體事物的確信無疑。
例如：He issure of success. 他自信會成功的。
I'm sure of his honesty. 我肯定他是誠實(shí)的。
However, he went on to explain that he was not sure about twothings ---- the grammar and some of the idioms.不過，他接著就解釋說，他在語法和某些習(xí)慣用語方面都沒多大把握。
If you are not sure about the situation in the world, you can readthe newspaper every day.如果你對世界形勢不大了解，你可以每天看看報紙。

若后面要接反身代詞，則只能用 be sure of, 即 be sure ofoneself,意為“有自信心”。
例如：Joanwill sit for an important examination next week, but she is notsure of herself. 瓊下周要參加一個重要考試，但她對自己沒有十分把握。

2. be sureto dosth，表示說話人對句子主語作出的判斷，認(rèn)為句子主語“必定”、“必然會”、“準(zhǔn)會”......。
例如： It issure to rain. 天一定會下雨。
He is sure to have known about that. 他準(zhǔn)會知道那件事。
He told me I was sure to get a warm welcome.他告訴我，說我準(zhǔn)會受到熱情接待的。

然而be sure to do用在祈使句中，不是表示判斷，而是表示對對方的要求，意為“務(wù)必要”，“一定要”。
例如： Besure not to forget it! 千萬別忘記呀！
Be sure to send my regards to your mother.務(wù)必代我問候你母親。
Be sure not to do that again. 一定不要再干那種事了。

3. be sure+賓語從句，表示主句主語對賓語從句中涉及的事物所作出的判斷，意為“確信某事一定會......”。
例如： I'mnot sure whether I've met him before.我不能確定以前是否見到過他。
We are sure he will make great progress this term.我們確信他這學(xué)期一定會取得巨大進(jìn)步

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